[InstCombine] lshr (mul (X, 2^N + 1)), N -> X when X is half-width #93677

AZero13 · 2024-05-29T12:58:18Z

Alive2 Proof:
https://alive2.llvm.org/ce/z/Yd2CKF

llvmbot · 2024-05-29T12:58:50Z

@llvm/pr-subscribers-llvm-transforms

Author: AtariDreams (AtariDreams)

Changes

Full diff: https://github.com/llvm/llvm-project/pull/93677.diff

3 Files Affected:

(modified) llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp (+66-7)
(modified) llvm/test/Transforms/InstCombine/ashr-lshr.ll (+281)
(modified) llvm/test/Transforms/InstCombine/lshr.ll (+28-8)

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp b/llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp
index 0f1979fbe0c76..3d2563317e336 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp
@@ -1461,13 +1461,30 @@ Instruction *InstCombinerImpl::visitLShr(BinaryOperator &I) {
 
     const APInt *MulC;
     if (match(Op0, m_NUWMul(m_Value(X), m_APInt(MulC)))) {
-      // Look for a "splat" mul pattern - it replicates bits across each half of
-      // a value, so a right shift is just a mask of the low bits:
-      // lshr i[2N] (mul nuw X, (2^N)+1), N --> and iN X, (2^N)-1
-      // TODO: Generalize to allow more than just half-width shifts?
-      if (BitWidth > 2 && ShAmtC * 2 == BitWidth && (*MulC - 1).isPowerOf2() &&
-          MulC->logBase2() == ShAmtC)
-        return BinaryOperator::CreateAnd(X, ConstantInt::get(Ty, *MulC - 2));
+      if (BitWidth > 2 && (*MulC - 1).isPowerOf2() &&
+          MulC->logBase2() == ShAmtC) {
+
+        // Look for a "splat" mul pattern - it replicates bits across each half
+        // of a value, so a right shift is just a mask of the low bits:
+        // lshr i[2N] (mul nuw X, (2^N)+1), N --> X
+        if (ShAmtC * 2 == BitWidth)
+          return replaceInstUsesWith(I, X);
+
+        KnownBits KnownX =
+            computeKnownBits(X, /* Depth */ 0, cast<Instruction>(Op0));
+        if (KnownX.countMaxActiveBits() <= ShAmtC)
+          return replaceInstUsesWith(I, X);
+
+        // lshr (mul nuw (X, 2^N + 1)), N -> add nuw (X, lshr(X, N))
+        if (Op0->hasOneUse()) {
+          auto *NewAdd = BinaryOperator::CreateNUWAdd(
+              X, Builder.CreateLShr(X, ConstantInt::get(Ty, ShAmtC), "",
+                                    I.isExact()));
+          NewAdd->setHasNoSignedWrap(
+              cast<OverflowingBinaryOperator>(Op0)->hasNoSignedWrap());
+          return NewAdd;
+        }
+      }
 
       // The one-use check is not strictly necessary, but codegen may not be
       // able to invert the transform and perf may suffer with an extra mul
@@ -1487,6 +1504,26 @@ Instruction *InstCombinerImpl::visitLShr(BinaryOperator &I) {
       }
     }
 
+    // lshr (mul nsw (X, 2^N + 1)), N -> add nsw (X, lshr(X, N))
+    if (match(Op0, m_OneUse(m_NSWMul(m_Value(X), m_APInt(MulC))))) {
+      if (BitWidth > 2 && (*MulC - 1).isPowerOf2() &&
+          MulC->logBase2() == ShAmtC) {
+        return BinaryOperator::CreateNSWAdd(
+            X, Builder.CreateLShr(X, ConstantInt::get(Ty, ShAmtC), "",
+                                  I.isExact()));
+      }
+    }
+
+    // lshr (mul nsw (X, 2^N + 1)), N -> add nsw (X, lshr(X, N))
+    if (match(Op0, m_OneUse(m_NSWMul(m_Value(X), m_APInt(MulC))))) {
+      if (BitWidth > 2 && (*MulC - 1).isPowerOf2() &&
+          MulC->logBase2() == ShAmtC) {
+        return BinaryOperator::CreateNSWAdd(
+            X, Builder.CreateLShr(X, ConstantInt::get(Ty, ShAmtC), "",
+                                  I.isExact()));
+      }
+    }
+
     // Try to narrow bswap.
     // In the case where the shift amount equals the bitwidth difference, the
     // shift is eliminated.
@@ -1690,6 +1727,28 @@ Instruction *InstCombinerImpl::visitAShr(BinaryOperator &I) {
       if (match(Op0, m_OneUse(m_NSWSub(m_Value(X), m_Value(Y)))))
         return new SExtInst(Builder.CreateICmpSLT(X, Y), Ty);
     }
+
+    const APInt *MulC;
+    if (match(Op0, m_NSWMul(m_Value(X), m_APInt(MulC))) &&
+        (BitWidth > 2 && (*MulC - 1).isPowerOf2() &&
+         MulC->logBase2() == ShAmt &&
+         (ShAmt < BitWidth - 1))) /* Minus 1 for the sign bit */ {
+
+      // ashr (mul nsw (X, 2^N + 1)), N -> add nsw (X, ashr(X, N))
+      KnownBits KnownX =
+          computeKnownBits(X, /* Depth */ 0, cast<Instruction>(Op0));
+      if (KnownX.countMaxActiveBits() <= ShAmt)
+        return replaceInstUsesWith(I, X);
+
+      if (Op0->hasOneUse()) {
+        auto *NewAdd = BinaryOperator::CreateNSWAdd(
+            X, Builder.CreateAShr(X, ConstantInt::get(Ty, ShAmt), "",
+                                  I.isExact()));
+        NewAdd->setHasNoUnsignedWrap(
+            cast<OverflowingBinaryOperator>(Op0)->hasNoUnsignedWrap());
+        return NewAdd;
+      }
+    }
   }
 
   const SimplifyQuery Q = SQ.getWithInstruction(&I);
diff --git a/llvm/test/Transforms/InstCombine/ashr-lshr.ll b/llvm/test/Transforms/InstCombine/ashr-lshr.ll
index ac206dc7999dd..f426755dfc9dd 100644
--- a/llvm/test/Transforms/InstCombine/ashr-lshr.ll
+++ b/llvm/test/Transforms/InstCombine/ashr-lshr.ll
@@ -604,3 +604,284 @@ define <2 x i8> @ashr_known_pos_exact_vec(<2 x i8> %x, <2 x i8> %y) {
   %r = ashr exact <2 x i8> %p, %y
   ret <2 x i8> %r
 }
+
+define i32 @lshr_mul_times_3_div_2(i32 %0) {
+; CHECK-LABEL: @lshr_mul_times_3_div_2(
+; CHECK-NEXT:    [[TMP2:%.*]] = lshr i32 [[TMP0:%.*]], 1
+; CHECK-NEXT:    [[LSHR:%.*]] = add nuw nsw i32 [[TMP2]], [[TMP0]]
+; CHECK-NEXT:    ret i32 [[LSHR]]
+;
+  %mul = mul nsw nuw i32 %0, 3
+  %lshr = lshr i32 %mul, 1
+  ret i32 %lshr
+}
+
+define i32 @lshr_mul_times_3_div_2_exact(i32 %x) {
+; CHECK-LABEL: @lshr_mul_times_3_div_2_exact(
+; CHECK-NEXT:    [[TMP1:%.*]] = lshr exact i32 [[X:%.*]], 1
+; CHECK-NEXT:    [[LSHR:%.*]] = add nsw i32 [[TMP1]], [[X]]
+; CHECK-NEXT:    ret i32 [[LSHR]]
+;
+  %mul = mul nsw i32 %x, 3
+  %lshr = lshr exact i32 %mul, 1
+  ret i32 %lshr
+}
+
+; Negative test
+
+define i32 @lshr_mul_times_3_div_2_no_flags(i32 %0) {
+; CHECK-LABEL: @lshr_mul_times_3_div_2_no_flags(
+; CHECK-NEXT:    [[MUL:%.*]] = mul i32 [[TMP0:%.*]], 3
+; CHECK-NEXT:    [[LSHR:%.*]] = lshr i32 [[MUL]], 1
+; CHECK-NEXT:    ret i32 [[LSHR]]
+;
+  %mul = mul i32 %0, 3
+  %lshr = lshr i32 %mul, 1
+  ret i32 %lshr
+}
+
+; Negative test
+
+define i32 @mul_times_3_div_2_multiuse_lshr(i32 %x) {
+; CHECK-LABEL: @mul_times_3_div_2_multiuse_lshr(
+; CHECK-NEXT:    [[MUL:%.*]] = mul nuw i32 [[X:%.*]], 3
+; CHECK-NEXT:    [[RES:%.*]] = lshr i32 [[MUL]], 1
+; CHECK-NEXT:    call void @use(i32 [[MUL]])
+; CHECK-NEXT:    ret i32 [[RES]]
+;
+  %mul = mul nuw i32 %x, 3
+  %res = lshr i32 %mul, 1
+  call void @use(i32 %mul)
+  ret i32 %res
+}
+
+define i32 @lshr_mul_times_3_div_2_exact_2(i32 %x) {
+; CHECK-LABEL: @lshr_mul_times_3_div_2_exact_2(
+; CHECK-NEXT:    [[TMP1:%.*]] = lshr exact i32 [[X:%.*]], 1
+; CHECK-NEXT:    [[LSHR:%.*]] = add nuw i32 [[TMP1]], [[X]]
+; CHECK-NEXT:    ret i32 [[LSHR]]
+;
+  %mul = mul nuw i32 %x, 3
+  %lshr = lshr exact i32 %mul, 1
+  ret i32 %lshr
+}
+
+define i32 @lshr_mul_times_5_div_4(i32 %0) {
+; CHECK-LABEL: @lshr_mul_times_5_div_4(
+; CHECK-NEXT:    [[TMP2:%.*]] = lshr i32 [[TMP0:%.*]], 2
+; CHECK-NEXT:    [[LSHR:%.*]] = add nuw nsw i32 [[TMP2]], [[TMP0]]
+; CHECK-NEXT:    ret i32 [[LSHR]]
+;
+  %mul = mul nsw nuw i32 %0, 5
+  %lshr = lshr i32 %mul, 2
+  ret i32 %lshr
+}
+
+define i32 @lshr_mul_times_5_div_4_exact(i32 %x) {
+; CHECK-LABEL: @lshr_mul_times_5_div_4_exact(
+; CHECK-NEXT:    [[TMP1:%.*]] = lshr exact i32 [[X:%.*]], 2
+; CHECK-NEXT:    [[LSHR:%.*]] = add nsw i32 [[TMP1]], [[X]]
+; CHECK-NEXT:    ret i32 [[LSHR]]
+;
+  %mul = mul nsw i32 %x, 5
+  %lshr = lshr exact i32 %mul, 2
+  ret i32 %lshr
+}
+
+; Negative test
+
+define i32 @lshr_mul_times_5_div_4_no_flags(i32 %0) {
+; CHECK-LABEL: @lshr_mul_times_5_div_4_no_flags(
+; CHECK-NEXT:    [[MUL:%.*]] = mul i32 [[TMP0:%.*]], 5
+; CHECK-NEXT:    [[LSHR:%.*]] = lshr i32 [[MUL]], 2
+; CHECK-NEXT:    ret i32 [[LSHR]]
+;
+  %mul = mul i32 %0, 5
+  %lshr = lshr i32 %mul, 2
+  ret i32 %lshr
+}
+
+; Negative test
+
+define i32 @mul_times_5_div_4_multiuse_lshr(i32 %x) {
+; CHECK-LABEL: @mul_times_5_div_4_multiuse_lshr(
+; CHECK-NEXT:    [[MUL:%.*]] = mul nuw i32 [[X:%.*]], 5
+; CHECK-NEXT:    [[RES:%.*]] = lshr i32 [[MUL]], 2
+; CHECK-NEXT:    call void @use(i32 [[MUL]])
+; CHECK-NEXT:    ret i32 [[RES]]
+;
+  %mul = mul nuw i32 %x, 5
+  %res = lshr i32 %mul, 2
+  call void @use(i32 %mul)
+  ret i32 %res
+}
+
+define i32 @lshr_mul_times_5_div_4_exact_2(i32 %x) {
+; CHECK-LABEL: @lshr_mul_times_5_div_4_exact_2(
+; CHECK-NEXT:    [[TMP1:%.*]] = lshr exact i32 [[X:%.*]], 2
+; CHECK-NEXT:    [[LSHR:%.*]] = add nuw i32 [[TMP1]], [[X]]
+; CHECK-NEXT:    ret i32 [[LSHR]]
+;
+  %mul = mul nuw i32 %x, 5
+  %lshr = lshr exact i32 %mul, 2
+  ret i32 %lshr
+}
+
+define i32 @ashr_mul_times_3_div_2(i32 %0) {
+; CHECK-LABEL: @ashr_mul_times_3_div_2(
+; CHECK-NEXT:    [[TMP2:%.*]] = ashr i32 [[TMP0:%.*]], 1
+; CHECK-NEXT:    [[ASHR:%.*]] = add nuw nsw i32 [[TMP2]], [[TMP0]]
+; CHECK-NEXT:    ret i32 [[ASHR]]
+;
+  %mul = mul nuw nsw i32 %0, 3
+  %ashr = ashr i32 %mul, 1
+  ret i32 %ashr
+}
+
+define i32 @ashr_mul_times_3_div_2_exact(i32 %x) {
+; CHECK-LABEL: @ashr_mul_times_3_div_2_exact(
+; CHECK-NEXT:    [[TMP1:%.*]] = ashr exact i32 [[X:%.*]], 1
+; CHECK-NEXT:    [[ASHR:%.*]] = add nsw i32 [[TMP1]], [[X]]
+; CHECK-NEXT:    ret i32 [[ASHR]]
+;
+  %mul = mul nsw i32 %x, 3
+  %ashr = ashr exact i32 %mul, 1
+  ret i32 %ashr
+}
+
+; Negative test
+
+define i32 @ashr_mul_times_3_div_2_no_flags(i32 %0) {
+; CHECK-LABEL: @ashr_mul_times_3_div_2_no_flags(
+; CHECK-NEXT:    [[MUL:%.*]] = mul i32 [[TMP0:%.*]], 3
+; CHECK-NEXT:    [[ASHR:%.*]] = ashr i32 [[MUL]], 1
+; CHECK-NEXT:    ret i32 [[ASHR]]
+;
+  %mul = mul i32 %0, 3
+  %ashr = ashr i32 %mul, 1
+  ret i32 %ashr
+}
+
+; Negative test
+
+define i32 @ashr_mul_times_3_div_2_no_nsw(i32 %0) {
+; CHECK-LABEL: @ashr_mul_times_3_div_2_no_nsw(
+; CHECK-NEXT:    [[MUL:%.*]] = mul nuw i32 [[TMP0:%.*]], 3
+; CHECK-NEXT:    [[ASHR:%.*]] = ashr i32 [[MUL]], 1
+; CHECK-NEXT:    ret i32 [[ASHR]]
+;
+  %mul = mul nuw i32 %0, 3
+  %ashr = ashr i32 %mul, 1
+  ret i32 %ashr
+}
+
+; Negative test
+
+define i32 @mul_times_3_div_2_multiuse_ashr(i32 %x) {
+; CHECK-LABEL: @mul_times_3_div_2_multiuse_ashr(
+; CHECK-NEXT:    [[MUL:%.*]] = mul nsw i32 [[X:%.*]], 3
+; CHECK-NEXT:    [[RES:%.*]] = ashr i32 [[MUL]], 1
+; CHECK-NEXT:    call void @use(i32 [[MUL]])
+; CHECK-NEXT:    ret i32 [[RES]]
+;
+  %mul = mul nsw i32 %x, 3
+  %res = ashr i32 %mul, 1
+  call void @use(i32 %mul)
+  ret i32 %res
+}
+
+define i32 @ashr_mul_times_3_div_2_exact_2(i32 %x) {
+; CHECK-LABEL: @ashr_mul_times_3_div_2_exact_2(
+; CHECK-NEXT:    [[TMP1:%.*]] = ashr exact i32 [[X:%.*]], 1
+; CHECK-NEXT:    [[ASHR:%.*]] = add nsw i32 [[TMP1]], [[X]]
+; CHECK-NEXT:    ret i32 [[ASHR]]
+;
+  %mul = mul nsw i32 %x, 3
+  %ashr = ashr exact i32 %mul, 1
+  ret i32 %ashr
+}
+
+define i32 @ashr_mul_times_5_div_4(i32 %0) {
+; CHECK-LABEL: @ashr_mul_times_5_div_4(
+; CHECK-NEXT:    [[TMP2:%.*]] = ashr i32 [[TMP0:%.*]], 2
+; CHECK-NEXT:    [[ASHR:%.*]] = add nuw nsw i32 [[TMP2]], [[TMP0]]
+; CHECK-NEXT:    ret i32 [[ASHR]]
+;
+  %mul = mul nuw nsw i32 %0, 5
+  %ashr = ashr i32 %mul, 2
+  ret i32 %ashr
+}
+
+define i32 @ashr_mul_times_5_div_4_exact(i32 %x) {
+; CHECK-LABEL: @ashr_mul_times_5_div_4_exact(
+; CHECK-NEXT:    [[TMP1:%.*]] = ashr exact i32 [[X:%.*]], 2
+; CHECK-NEXT:    [[ASHR:%.*]] = add nsw i32 [[TMP1]], [[X]]
+; CHECK-NEXT:    ret i32 [[ASHR]]
+;
+  %mul = mul nsw i32 %x, 5
+  %ashr = ashr exact i32 %mul, 2
+  ret i32 %ashr
+}
+
+; Negative test
+
+define i32 @ashr_mul_times_5_div_4_no_flags(i32 %0) {
+; CHECK-LABEL: @ashr_mul_times_5_div_4_no_flags(
+; CHECK-NEXT:    [[MUL:%.*]] = mul i32 [[TMP0:%.*]], 5
+; CHECK-NEXT:    [[ASHR:%.*]] = ashr i32 [[MUL]], 2
+; CHECK-NEXT:    ret i32 [[ASHR]]
+;
+  %mul = mul i32 %0, 5
+  %ashr = ashr i32 %mul, 2
+  ret i32 %ashr
+}
+
+; Negative test
+
+define i32 @mul_times_5_div_4_multiuse_ashr(i32 %x) {
+; CHECK-LABEL: @mul_times_5_div_4_multiuse_ashr(
+; CHECK-NEXT:    [[MUL:%.*]] = mul nsw i32 [[X:%.*]], 5
+; CHECK-NEXT:    [[RES:%.*]] = ashr i32 [[MUL]], 2
+; CHECK-NEXT:    call void @use(i32 [[MUL]])
+; CHECK-NEXT:    ret i32 [[RES]]
+;
+  %mul = mul nsw i32 %x, 5
+  %res = ashr i32 %mul, 2
+  call void @use(i32 %mul)
+  ret i32 %res
+}
+
+define i32 @ashr_mul_times_5_div_4_exact_2(i32 %x) {
+; CHECK-LABEL: @ashr_mul_times_5_div_4_exact_2(
+; CHECK-NEXT:    [[TMP1:%.*]] = ashr exact i32 [[X:%.*]], 2
+; CHECK-NEXT:    [[ASHR:%.*]] = add nsw i32 [[TMP1]], [[X]]
+; CHECK-NEXT:    ret i32 [[ASHR]]
+;
+  %mul = mul nsw i32 %x, 5
+  %ashr = ashr exact i32 %mul, 2
+  ret i32 %ashr
+}
+
+define i32 @mul_splat_fold_known_active_bits(i32 %x) {
+; CHECK-LABEL: @mul_splat_fold_known_active_bits(
+; CHECK-NEXT:    [[XX:%.*]] = and i32 [[X:%.*]], 360
+; CHECK-NEXT:    ret i32 [[XX]]
+;
+  %xx = and i32 %x, 360
+  %m = mul nuw i32 %xx, 65537
+  %t = ashr i32 %m, 16
+  ret i32 %t
+}
+
+define i32 @mul_splat_fold_no_known_active_bits(i32 %x) {
+; CHECK-LABEL: @mul_splat_fold_no_known_active_bits(
+; CHECK-NEXT:    [[TMP1:%.*]] = ashr i32 [[X:%.*]], 16
+; CHECK-NEXT:    [[T:%.*]] = add nsw i32 [[TMP1]], [[X]]
+; CHECK-NEXT:    ret i32 [[T]]
+;
+  %m = mul nsw i32 %x, 65537
+  %t = ashr i32 %m, 16
+  ret i32 %t
+}
+
+declare void @use(i32)
diff --git a/llvm/test/Transforms/InstCombine/lshr.ll b/llvm/test/Transforms/InstCombine/lshr.ll
index fa92c1c4b3be4..17b08985ee90e 100644
--- a/llvm/test/Transforms/InstCombine/lshr.ll
+++ b/llvm/test/Transforms/InstCombine/lshr.ll
@@ -348,22 +348,31 @@ define <2 x i32> @narrow_lshr_constant(<2 x i8> %x, <2 x i8> %y) {
 
 define i32 @mul_splat_fold(i32 %x) {
 ; CHECK-LABEL: @mul_splat_fold(
-; CHECK-NEXT:    [[T:%.*]] = and i32 [[X:%.*]], 65535
-; CHECK-NEXT:    ret i32 [[T]]
+; CHECK-NEXT:    ret i32 [[X:%.*]]
 ;
   %m = mul nuw i32 %x, 65537
   %t = lshr i32 %m, 16
   ret i32 %t
 }
 
+define i32 @mul_splat_fold_known_zeros(i32 %x) {
+; CHECK-LABEL: @mul_splat_fold_known_zeros(
+; CHECK-NEXT:    [[XX:%.*]] = and i32 [[X:%.*]], 360
+; CHECK-NEXT:    ret i32 [[XX]]
+;
+  %xx = and i32 %x, 360
+  %m = mul nuw i32 %xx, 65537
+  %t = lshr i32 %m, 16
+  ret i32 %t
+}
+
 ; Vector type, extra use, weird types are all ok.
 
 define <3 x i14> @mul_splat_fold_vec(<3 x i14> %x) {
 ; CHECK-LABEL: @mul_splat_fold_vec(
 ; CHECK-NEXT:    [[M:%.*]] = mul nuw <3 x i14> [[X:%.*]], <i14 129, i14 129, i14 129>
 ; CHECK-NEXT:    call void @usevec(<3 x i14> [[M]])
-; CHECK-NEXT:    [[T:%.*]] = and <3 x i14> [[X]], <i14 127, i14 127, i14 127>
-; CHECK-NEXT:    ret <3 x i14> [[T]]
+; CHECK-NEXT:    ret <3 x i14> [[X]]
 ;
   %m = mul nuw <3 x i14> %x, <i14 129, i14 129, i14 129>
   call void @usevec(<3 x i14> %m)
@@ -628,12 +637,10 @@ define i32 @mul_splat_fold_wrong_lshr_const(i32 %x) {
   ret i32 %t
 }
 
-; Negative test
-
 define i32 @mul_splat_fold_no_nuw(i32 %x) {
 ; CHECK-LABEL: @mul_splat_fold_no_nuw(
-; CHECK-NEXT:    [[M:%.*]] = mul nsw i32 [[X:%.*]], 65537
-; CHECK-NEXT:    [[T:%.*]] = lshr i32 [[M]], 16
+; CHECK-NEXT:    [[TMP1:%.*]] = lshr i32 [[X:%.*]], 16
+; CHECK-NEXT:    [[T:%.*]] = add nsw i32 [[TMP1]], [[X]]
 ; CHECK-NEXT:    ret i32 [[T]]
 ;
   %m = mul nsw i32 %x, 65537
@@ -641,6 +648,19 @@ define i32 @mul_splat_fold_no_nuw(i32 %x) {
   ret i32 %t
 }
 
+; Negative test
+
+define i32 @mul_splat_fold_no_flags(i32 %x) {
+; CHECK-LABEL: @mul_splat_fold_no_flags(
+; CHECK-NEXT:    [[M:%.*]] = mul i32 [[X:%.*]], 65537
+; CHECK-NEXT:    [[T:%.*]] = lshr i32 [[M]], 16
+; CHECK-NEXT:    ret i32 [[T]]
+;
+  %m = mul i32 %x, 65537
+  %t = lshr i32 %m, 16
+  ret i32 %t
+}
+
 ; Negative test (but simplifies before we reach the mul_splat transform)- need more than 2 bits
 
 define i2 @mul_splat_fold_too_narrow(i2 %x) {

llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp

nikic · 2024-05-29T13:15:23Z

If you want to create a draft pull request, please create it as a draft. Do not first open it as a normal pull request and then convert it into a draft. Otherwise you will still notify and subscribe everyone.

AZero13 · 2024-05-29T13:29:22Z

I have used this platform for years and today I learned you could do that instead of converting to draft. I'm so sorry I feel so dumb.

github-actions · 2024-05-29T21:18:01Z

✅ With the latest revision this PR passed the C/C++ code formatter.

llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp

Alive2 Proofs: https://alive2.llvm.org/ce/z/eSinJY https://alive2.llvm.org/ce/z/sweDgc https://alive2.llvm.org/ce/z/-2dXZi https://alive2.llvm.org/ce/z/kx2PhF https://alive2.llvm.org/ce/z/e9QjM6

nikic

LGTM

AZero13 requested a review from nikic as a code owner May 29, 2024 12:58

llvmbot added the llvm:transforms label May 29, 2024

AZero13 marked this pull request as draft May 29, 2024 13:01

nikic reviewed May 29, 2024

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llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp Outdated Show resolved Hide resolved

AZero13 force-pushed the d branch from 728eac9 to d3e88aa Compare May 29, 2024 22:27

AZero13 changed the title ~~[InstCombine] Simplify further when shift is half bitwidth~~ [InstCombine] lshr (mul (X, 2^N + 1)), N -> X when X is half-width May 29, 2024

AZero13 requested a review from nikic May 29, 2024 22:28

AZero13 marked this pull request as ready for review May 29, 2024 22:28

topperc reviewed May 29, 2024

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llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp Outdated Show resolved Hide resolved

AZero13 force-pushed the d branch from d3e88aa to babcee1 Compare May 29, 2024 22:36

AZero13 requested a review from topperc May 29, 2024 22:37

AZero13 force-pushed the d branch 4 times, most recently from f9bdb00 to 3846e27 Compare May 30, 2024 03:01

[InstCombine] lshr (mul (X, 2^N + 1)), N -> X when X is half-width

7fb3cf5

Alive2 Proofs: https://alive2.llvm.org/ce/z/eSinJY https://alive2.llvm.org/ce/z/sweDgc https://alive2.llvm.org/ce/z/-2dXZi https://alive2.llvm.org/ce/z/kx2PhF https://alive2.llvm.org/ce/z/e9QjM6

AZero13 force-pushed the d branch from 3846e27 to 7fb3cf5 Compare May 30, 2024 03:10

nikic approved these changes May 30, 2024

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nikic merged commit 1034b4d into llvm:main May 30, 2024
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AZero13 deleted the d branch May 30, 2024 11:29

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[InstCombine] lshr (mul (X, 2^N + 1)), N -> X when X is half-width #93677

[InstCombine] lshr (mul (X, 2^N + 1)), N -> X when X is half-width #93677

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AZero13 commented May 29, 2024 •

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[InstCombine] lshr (mul (X, 2^N + 1)), N -> X when X is half-width #93677

[InstCombine] lshr (mul (X, 2^N + 1)), N -> X when X is half-width #93677

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AZero13 commented May 29, 2024 •

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