[SimplifyLibCalls] Constant fold `remquo` #99647

dtcxzyw · 2024-07-19T13:14:52Z

This patch adds constant folding support for remquo.
Reference: https://en.cppreference.com/w/cpp/numeric/math/remquo

Closes #99497.

llvmbot · 2024-07-19T13:15:23Z

@llvm/pr-subscribers-llvm-transforms

Author: Yingwei Zheng (dtcxzyw)

Changes

This patch adds constant folding support for remquo.
Reference: https://en.cppreference.com/w/cpp/numeric/math/remquo

Closes #99497.

Full diff: https://github.com/llvm/llvm-project/pull/99647.diff

3 Files Affected:

(modified) llvm/include/llvm/Transforms/Utils/SimplifyLibCalls.h (+1)
(modified) llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp (+33)
(added) llvm/test/Transforms/InstCombine/remquo.ll (+116)

diff --git a/llvm/include/llvm/Transforms/Utils/SimplifyLibCalls.h b/llvm/include/llvm/Transforms/Utils/SimplifyLibCalls.h
index e2682b429e9db..770da12e01233 100644
--- a/llvm/include/llvm/Transforms/Utils/SimplifyLibCalls.h
+++ b/llvm/include/llvm/Transforms/Utils/SimplifyLibCalls.h
@@ -205,6 +205,7 @@ class LibCallSimplifier {
   Value *optimizeSinCosPi(CallInst *CI, bool IsSin, IRBuilderBase &B);
   Value *optimizeTrigInversionPairs(CallInst *CI, IRBuilderBase &B);
   Value *optimizeSymmetric(CallInst *CI, LibFunc Func, IRBuilderBase &B);
+  Value *optimizeRemquo(CallInst *CI, IRBuilderBase &B);
   // Wrapper for all floating point library call optimizations
   Value *optimizeFloatingPointLibCall(CallInst *CI, LibFunc Func,
                                       IRBuilderBase &B);
diff --git a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp b/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
index 89c8c5bf08954..f62c53c208f9f 100644
--- a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
@@ -3018,6 +3018,35 @@ void LibCallSimplifier::classifyArgUse(
   }
 }
 
+/// Constant folds remquo
+Value *LibCallSimplifier::optimizeRemquo(CallInst *CI, IRBuilderBase &B) {
+  const APFloat *X, *Y;
+  if (!match(CI->getArgOperand(0), m_APFloat(X)) || !match(CI->getArgOperand(1), m_APFloat(Y)))
+    return nullptr;
+
+  if (X->isNaN() || Y->isNaN() || X->isInfinity() || Y->isZero())
+    return nullptr;
+
+  APFloat::opStatus Status;
+  APFloat Quot = *X;
+  Status = Quot.divide(*Y, APFloat::rmNearestTiesToEven);
+  if (Status != APFloat::opOK && Status != APFloat::opInexact)
+    return nullptr;
+  APFloat Rem = *X;
+  if (Rem.remainder(*Y) != APFloat::opOK)
+    return nullptr;
+
+  // TODO: We can only keep at least the three of the last bits of x/y
+  APSInt QuotInt(32, /*isUnsigned=*/false);
+  bool IsExact;
+  Status = Quot.convertToInteger(QuotInt, APFloat::rmNearestTiesToEven, &IsExact);
+  if (Status != APFloat::opOK || Status != APFloat::opInexact)
+    return nullptr;
+
+  B.CreateAlignedStore(ConstantInt::get(B.getInt32Ty(), QuotInt.getExtValue()), CI->getArgOperand(2), CI->getParamAlign(2));
+  return ConstantFP::get(CI->getType(), Rem);
+}
+
 //===----------------------------------------------------------------------===//
 // Integer Library Call Optimizations
 //===----------------------------------------------------------------------===//
@@ -3926,6 +3955,10 @@ Value *LibCallSimplifier::optimizeFloatingPointLibCall(CallInst *CI,
   case LibFunc_cabsf:
   case LibFunc_cabsl:
     return optimizeCAbs(CI, Builder);
+  case LibFunc_remquo:
+  case LibFunc_remquof:
+  case LibFunc_remquol:
+    return optimizeRemquo(CI, Builder);
   default:
     return nullptr;
   }
diff --git a/llvm/test/Transforms/InstCombine/remquo.ll b/llvm/test/Transforms/InstCombine/remquo.ll
new file mode 100644
index 0000000000000..691086ac1c8f7
--- /dev/null
+++ b/llvm/test/Transforms/InstCombine/remquo.ll
@@ -0,0 +1,116 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt < %s -passes=instcombine -S | FileCheck %s
+
+define float @remquo_f32(ptr %quo) {
+; CHECK-LABEL: define float @remquo_f32(
+; CHECK-SAME: ptr [[QUO:%.*]]) {
+; CHECK-NEXT:  [[ENTRY:.*:]]
+; CHECK-NEXT:    store i32 -2, ptr [[QUO]], align 4
+; CHECK-NEXT:    ret float 1.000000e+00
+;
+entry:
+  %call = call float @remquof(float -5.000000e+00, float 3.000000e+00, ptr %quo)
+  ret float %call
+}
+
+define float @remquo_f32_quo_sign(ptr %quo) {
+; CHECK-LABEL: define float @remquo_f32_quo_sign(
+; CHECK-SAME: ptr [[QUO:%.*]]) {
+; CHECK-NEXT:  [[ENTRY:.*:]]
+; CHECK-NEXT:    store i32 2, ptr [[QUO]], align 4
+; CHECK-NEXT:    ret float -1.000000e+00
+;
+entry:
+  %call = call float @remquof(float 5.000000e+00, float 3.000000e+00, ptr %quo)
+  ret float %call
+}
+
+define float @remquo_f32_round(ptr %quo) {
+; CHECK-LABEL: define float @remquo_f32_round(
+; CHECK-SAME: ptr [[QUO:%.*]]) {
+; CHECK-NEXT:  [[ENTRY:.*:]]
+; CHECK-NEXT:    store i32 -6, ptr [[QUO]], align 4
+; CHECK-NEXT:    ret float 0xBFC9999900000000
+;
+entry:
+  %call = call float @remquof(float -5.000000e+00, float 0x3FE99999A0000000, ptr %quo)
+  ret float %call
+}
+
+define double @remquo_f64(ptr %quo) {
+; CHECK-LABEL: define double @remquo_f64(
+; CHECK-SAME: ptr [[QUO:%.*]]) {
+; CHECK-NEXT:  [[ENTRY:.*:]]
+; CHECK-NEXT:    store i32 -5, ptr [[QUO]], align 4
+; CHECK-NEXT:    ret double -0.000000e+00
+;
+entry:
+  %call = call double @remquo(double -5.000000e+00, double 1.000000e+00, ptr %quo)
+  ret double %call
+}
+
+define double @remquo_f80(ptr %quo) {
+; CHECK-LABEL: define double @remquo_f80(
+; CHECK-SAME: ptr [[QUO:%.*]]) {
+; CHECK-NEXT:  [[ENTRY:.*:]]
+; CHECK-NEXT:    [[CALL:%.*]] = call double @remquol(x86_fp80 0xKC001A000000000000000, x86_fp80 0xK4000C000000000000000, ptr [[QUO]])
+; CHECK-NEXT:    ret double [[CALL]]
+;
+entry:
+  %call = call double @remquol(x86_fp80 0xKC001A000000000000000, x86_fp80 0xK4000C000000000000000, ptr %quo)
+  ret double %call
+}
+
+; Negative tests
+
+define float @remquo_f32_inf_x(ptr %quo) {
+; CHECK-LABEL: define float @remquo_f32_inf_x(
+; CHECK-SAME: ptr [[QUO:%.*]]) {
+; CHECK-NEXT:  [[ENTRY:.*:]]
+; CHECK-NEXT:    [[CALL:%.*]] = call float @remquof(float 0x7FF0000000000000, float 1.000000e+00, ptr [[QUO]])
+; CHECK-NEXT:    ret float [[CALL]]
+;
+entry:
+  %call = call float @remquof(float 0x7FF0000000000000, float 1.000000e+00, ptr %quo)
+  ret float %call
+}
+
+define float @remquo_f32_zero_y(ptr %quo) {
+; CHECK-LABEL: define float @remquo_f32_zero_y(
+; CHECK-SAME: ptr [[QUO:%.*]]) {
+; CHECK-NEXT:  [[ENTRY:.*:]]
+; CHECK-NEXT:    [[CALL:%.*]] = call float @remquof(float -5.000000e+00, float 0.000000e+00, ptr [[QUO]])
+; CHECK-NEXT:    ret float [[CALL]]
+;
+entry:
+  %call = call float @remquof(float -5.000000e+00, float 0.000000e+00, ptr %quo)
+  ret float %call
+}
+
+define float @remquo_f32_nan_x(ptr %quo) {
+; CHECK-LABEL: define float @remquo_f32_nan_x(
+; CHECK-SAME: ptr [[QUO:%.*]]) {
+; CHECK-NEXT:  [[ENTRY:.*:]]
+; CHECK-NEXT:    [[CALL:%.*]] = call float @remquof(float 0x7FF8000000000000, float 1.000000e+00, ptr [[QUO]])
+; CHECK-NEXT:    ret float [[CALL]]
+;
+entry:
+  %call = call float @remquof(float 0x7FF8000000000000, float 1.000000e+00, ptr %quo)
+  ret float %call
+}
+
+define float @remquo_f32_nan_y(ptr %quo) {
+; CHECK-LABEL: define float @remquo_f32_nan_y(
+; CHECK-SAME: ptr [[QUO:%.*]]) {
+; CHECK-NEXT:  [[ENTRY:.*:]]
+; CHECK-NEXT:    [[CALL:%.*]] = call float @remquof(float 1.000000e+00, float 0x7FF8000000000000, ptr [[QUO]])
+; CHECK-NEXT:    ret float [[CALL]]
+;
+entry:
+  %call = call float @remquof(float 1.000000e+00, float 0x7FF8000000000000, ptr %quo)
+  ret float %call
+}
+
+declare float @remquof(float, float, ptr)
+declare double @remquo(double, double, ptr)
+declare x86_fp80 @remquol(x86_fp80, x86_fp80, ptr)

dtcxzyw · 2024-07-19T13:17:26Z

llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp

+  if (Rem.remainder(*Y) != APFloat::opOK)
+    return nullptr;
+
+  // TODO: We can only keep at least the three of the last bits of x/y


The current implementation is slightly conservative. The integer part of x/y may be out of range of i32.

github-actions · 2024-07-19T13:18:33Z

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

arsenm · 2024-07-19T13:28:23Z

llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp

+  APFloat::opStatus Status;
+  APFloat Quot = *X;
+  Status = Quot.divide(*Y, APFloat::rmNearestTiesToEven);
+  if (Status != APFloat::opOK && Status != APFloat::opInexact)
+    return nullptr;
+  APFloat Rem = *X;
+  if (Rem.remainder(*Y) != APFloat::opOK)
+    return nullptr;
+
+  // TODO: We can only keep at least the three of the last bits of x/y
+  APSInt QuotInt(32, /*isUnsigned=*/false);
+  bool IsExact;
+  Status = Quot.convertToInteger(QuotInt, APFloat::rmNearestTiesToEven, &IsExact);
+  if (Status != APFloat::opOK || Status != APFloat::opInexact)
+    return nullptr;


Should pull the actual implementation into APFloat

See #99647 (comment). The current implementation doesn't match the standard behavior. I don't think it's appropriate to move these logic into APFloat.

llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp

llvm/test/Transforms/InstCombine/remquo.ll

llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp

llvm/test/Transforms/InstCombine/remquo.ll

arsenm · 2024-07-21T08:18:40Z

Typo in title

arsenm · 2024-07-23T18:18:09Z

llvm/test/Transforms/InstCombine/remquo.ll

+  ret float %call
+}
+
+declare float @remquof(float, float, ptr)


Need a non-edgcase strictfp case?

See remquo_f32_strictfp

Summary: This patch adds constant folding support for `remquo`. Reference: https://en.cppreference.com/w/cpp/numeric/math/remquo Closes #99497. Test Plan: Reviewers: Subscribers: Tasks: Tags: Differential Revision: https://phabricator.intern.facebook.com/D60250753

[SimplfiyLibCalls] Constant fold remquo

3ca0346

dtcxzyw requested review from arsenm, andykaylor and jcranmer-intel July 19, 2024 13:14

llvmbot added the llvm:transforms label Jul 19, 2024

dtcxzyw commented Jul 19, 2024

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arsenm reviewed Jul 19, 2024

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arsenm reviewed Jul 19, 2024

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dtcxzyw added 2 commits July 19, 2024 21:31

[SimplifyLibCalls] Fix typo

5034ef4

[SimplifyLibCalls] Address review comments.

96a0ef3

arsenm reviewed Jul 19, 2024

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dtcxzyw commented Jul 19, 2024

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[SimplifyLibCalls] Put remquol variants into separate files. NFC.

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arsenm reviewed Jul 21, 2024

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dtcxzyw changed the title ~~[SimplfiyLibCalls] Constant fold remquo~~ [SimplifyLibCalls] Constant fold remquo Jul 21, 2024

dtcxzyw added 3 commits July 22, 2024 18:24

[SimplifyLibCalls] Add more tests. NFC.

f6adf3b

[SimplifyLibCalls] Format code. NFC.

4584775

[SimplifyLibCalls] Address review comments. NFC.

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arsenm reviewed Jul 23, 2024

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arsenm added the floating-point Floating-point math label Jul 23, 2024

arsenm approved these changes Jul 23, 2024

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dtcxzyw merged commit 9d45b45 into llvm:main Jul 24, 2024
6 of 8 checks passed

dtcxzyw deleted the remquo-support-part2 branch July 24, 2024 05:32

dtcxzyw mentioned this pull request Aug 5, 2024

log1p(x), logb(x), ilogb(x) are not folded at the compilation time when x is constant #101873

Closed

fawdlstty mentioned this pull request Oct 28, 2024

llrint(x) are not folded at the compilation time when (x) is constant #113914

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