[CVP] Canonicalize signed minmax into unsigned

Author: dtcxzyw

llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp

@@ -90,6 +90,8 @@ STATISTIC(NumSaturating,
     "Number of saturating arithmetics converted to normal arithmetics");
 STATISTIC(NumNonNull, "Number of function pointer arguments marked non-null");
 STATISTIC(NumMinMax, "Number of llvm.[us]{min,max} intrinsics removed");
+STATISTIC(NumSMinMax,
+          "Number of llvm.s{min,max} intrinsics simplified to unsigned");
 STATISTIC(NumUDivURemsNarrowedExpanded,
           "Number of bound udiv's/urem's expanded");
 STATISTIC(NumZExt, "Number of non-negative deductions");
@@ -528,17 +530,35 @@ static bool processAbsIntrinsic(IntrinsicInst *II, LazyValueInfo *LVI) {
 }
 
 // See if this min/max intrinsic always picks it's one specific operand.
+// If not, check whether we can canonicalize signed minmax into unsigned version
 static bool processMinMaxIntrinsic(MinMaxIntrinsic *MM, LazyValueInfo *LVI) {
   CmpInst::Predicate Pred = CmpInst::getNonStrictPredicate(MM->getPredicate());
   LazyValueInfo::Tristate Result = LVI->getPredicateAt(
       Pred, MM->getLHS(), MM->getRHS(), MM, /*UseBlockValue=*/true);
-  if (Result == LazyValueInfo::Unknown)
-    return false;
+  if (Result != LazyValueInfo::Unknown) {
+    ++NumMinMax;
+    MM->replaceAllUsesWith(MM->getOperand(!Result));
+    MM->eraseFromParent();
+    return true;
+  }
 
-  ++NumMinMax;
-  MM->replaceAllUsesWith(MM->getOperand(!Result));
-  MM->eraseFromParent();
-  return true;
+  if (MM->isSigned() &&
+      ConstantRange::areInsensitiveToSignednessOfICmpPredicate(
+          LVI->getConstantRangeAtUse(MM->getOperandUse(0),
+                                     /*UndefAllowed*/ true),
+          LVI->getConstantRangeAtUse(MM->getOperandUse(1),
+                                     /*UndefAllowed*/ true))) {
+    ++NumSMinMax;
+    IRBuilder<> B(MM);
+    MM->replaceAllUsesWith(B.CreateBinaryIntrinsic(
+        MM->getIntrinsicID() == Intrinsic::smin ? Intrinsic::umin
+                                                : Intrinsic::umax,
+        MM->getLHS(), MM->getRHS()));
+    MM->eraseFromParent();
+    return true;
+  }
+
+  return false;
 }
 
 // Rewrite this with.overflow intrinsic as non-overflowing.

llvm/test/Transforms/CorrelatedValuePropagation/min-max.ll

@@ -167,7 +167,7 @@ define i8 @test14(i8 %x) {
 ; CHECK-LABEL: @test14(
 ; CHECK-NEXT:    [[LIM:%.*]] = icmp sge i8 [[X:%.*]], 42
 ; CHECK-NEXT:    call void @llvm.assume(i1 [[LIM]])
-; CHECK-NEXT:    [[R:%.*]] = call i8 @llvm.smin.i8(i8 [[X]], i8 42)
+; CHECK-NEXT:    [[TMP1:%.*]] = call i8 @llvm.umin.i8(i8 [[X]], i8 42)
 ; CHECK-NEXT:    ret i8 42
 ;
   %lim = icmp sge i8 %x, 42
@@ -179,8 +179,8 @@ define i8 @test15(i8 %x) {
 ; CHECK-LABEL: @test15(
 ; CHECK-NEXT:    [[LIM:%.*]] = icmp sge i8 [[X:%.*]], 41
 ; CHECK-NEXT:    call void @llvm.assume(i1 [[LIM]])
-; CHECK-NEXT:    [[R:%.*]] = call i8 @llvm.smin.i8(i8 [[X]], i8 42)
-; CHECK-NEXT:    ret i8 [[R]]
+; CHECK-NEXT:    [[TMP1:%.*]] = call i8 @llvm.umin.i8(i8 [[X]], i8 42)
+; CHECK-NEXT:    ret i8 [[TMP1]]
 ;
   %lim = icmp sge i8 %x, 41
   call void @llvm.assume(i1 %lim)
@@ -192,8 +192,8 @@ define i8 @test16(i8 %x) {
 ; CHECK-LABEL: @test16(
 ; CHECK-NEXT:    [[LIM:%.*]] = icmp sge i8 [[X:%.*]], 41
 ; CHECK-NEXT:    call void @llvm.assume(i1 [[LIM]])
-; CHECK-NEXT:    [[R:%.*]] = call i8 @llvm.smax.i8(i8 [[X]], i8 42)
-; CHECK-NEXT:    ret i8 [[R]]
+; CHECK-NEXT:    [[TMP1:%.*]] = call i8 @llvm.umax.i8(i8 [[X]], i8 42)
+; CHECK-NEXT:    ret i8 [[TMP1]]
 ;
   %lim = icmp sge i8 %x, 41
   call void @llvm.assume(i1 %lim)
@@ -240,8 +240,8 @@ define i8 @test_smax_to_umax_nneg(i8 %a, i8 %b) {
 ; CHECK-LABEL: @test_smax_to_umax_nneg(
 ; CHECK-NEXT:    [[NNEG_A:%.*]] = and i8 [[A:%.*]], 127
 ; CHECK-NEXT:    [[NNEG_B:%.*]] = and i8 [[B:%.*]], 127
-; CHECK-NEXT:    [[RET:%.*]] = call i8 @llvm.smax.i8(i8 [[NNEG_A]], i8 [[NNEG_B]])
-; CHECK-NEXT:    ret i8 [[RET]]
+; CHECK-NEXT:    [[TMP1:%.*]] = call i8 @llvm.umax.i8(i8 [[NNEG_A]], i8 [[NNEG_B]])
+; CHECK-NEXT:    ret i8 [[TMP1]]
 ;
   %nneg_a = and i8 %a, 127
   %nneg_b = and i8 %b, 127
@@ -253,8 +253,8 @@ define i8 @test_smax_to_umax_neg(i8 %a, i8 %b) {
 ; CHECK-LABEL: @test_smax_to_umax_neg(
 ; CHECK-NEXT:    [[NEG_A:%.*]] = or i8 [[A:%.*]], -128
 ; CHECK-NEXT:    [[NEG_B:%.*]] = or i8 [[B:%.*]], -128
-; CHECK-NEXT:    [[RET:%.*]] = call i8 @llvm.smax.i8(i8 [[NEG_A]], i8 [[NEG_B]])
-; CHECK-NEXT:    ret i8 [[RET]]
+; CHECK-NEXT:    [[TMP1:%.*]] = call i8 @llvm.umax.i8(i8 [[NEG_A]], i8 [[NEG_B]])
+; CHECK-NEXT:    ret i8 [[TMP1]]
 ;
   %neg_a = or i8 %a, 128
   %neg_b = or i8 %b, 128
@@ -266,8 +266,8 @@ define i8 @test_smin_to_umin_nneg(i8 %a, i8 %b) {
 ; CHECK-LABEL: @test_smin_to_umin_nneg(
 ; CHECK-NEXT:    [[NNEG_A:%.*]] = and i8 [[A:%.*]], 127
 ; CHECK-NEXT:    [[NNEG_B:%.*]] = and i8 [[B:%.*]], 127
-; CHECK-NEXT:    [[RET:%.*]] = call i8 @llvm.smin.i8(i8 [[NNEG_A]], i8 [[NNEG_B]])
-; CHECK-NEXT:    ret i8 [[RET]]
+; CHECK-NEXT:    [[TMP1:%.*]] = call i8 @llvm.umin.i8(i8 [[NNEG_A]], i8 [[NNEG_B]])
+; CHECK-NEXT:    ret i8 [[TMP1]]
 ;
   %nneg_a = and i8 %a, 127
   %nneg_b = and i8 %b, 127
@@ -279,8 +279,8 @@ define i8 @test_smin_to_umin_neg(i8 %a, i8 %b) {
 ; CHECK-LABEL: @test_smin_to_umin_neg(
 ; CHECK-NEXT:    [[NEG_A:%.*]] = or i8 [[A:%.*]], -128
 ; CHECK-NEXT:    [[NEG_B:%.*]] = or i8 [[B:%.*]], -128
-; CHECK-NEXT:    [[RET:%.*]] = call i8 @llvm.smin.i8(i8 [[NEG_A]], i8 [[NEG_B]])
-; CHECK-NEXT:    ret i8 [[RET]]
+; CHECK-NEXT:    [[TMP1:%.*]] = call i8 @llvm.umin.i8(i8 [[NEG_A]], i8 [[NEG_B]])
+; CHECK-NEXT:    ret i8 [[TMP1]]
 ;
   %neg_a = or i8 %a, 128
   %neg_b = or i8 %b, 128