[llvm] [InstCombine] Fold (X * 0.0) * constant => X * 0.0 #85241 (PR #92512)

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Sun May 19 02:20:31 PDT 2024


https://github.com/SahilPatidar updated https://github.com/llvm/llvm-project/pull/92512

>From 5487445caa8a93be86385441371f0e4b5ae8a141 Mon Sep 17 00:00:00 2001
From: SahilPatidar <patidarsahil2001 at gmail.com>
Date: Wed, 27 Mar 2024 22:39:29 +0530
Subject: [PATCH 1/2] [InstCombine] Fold (X * 0.0) * constant => X * 0.0

---
 .../InstCombine/InstCombineMulDivRem.cpp      |  9 +++
 llvm/test/Transforms/InstCombine/fmul.ll      | 60 +++++++++++++++++++
 2 files changed, 69 insertions(+)

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
index ca1b1921404d8..3da1ac909d974 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
@@ -905,6 +905,15 @@ Instruction *InstCombinerImpl::visitFMul(BinaryOperator &I) {
     }
   }
 
+  // (X * 0.0) * constant => X * 0.0
+  if (match(Op0, m_FMul(m_Value(X), m_AnyZeroFP())) &&
+      match(Op1, m_Constant())) {
+    Instruction *FI = cast<Instruction>(Op0);
+    replaceOperand(*FI, 0, Op1);
+    replaceOperand(I, 1, Op0);
+    return replaceOperand(I, 0, X);
+  }
+
   // Simplify FMUL recurrences starting with 0.0 to 0.0 if nnan and nsz are set.
   // Given a phi node with entry value as 0 and it used in fmul operation,
   // we can replace fmul with 0 safely and eleminate loop operation.
diff --git a/llvm/test/Transforms/InstCombine/fmul.ll b/llvm/test/Transforms/InstCombine/fmul.ll
index 1526956c5b241..4ddbbbc622085 100644
--- a/llvm/test/Transforms/InstCombine/fmul.ll
+++ b/llvm/test/Transforms/InstCombine/fmul.ll
@@ -1407,3 +1407,63 @@ entry:
   %ret = fmul <3 x float> %a, <float -0.0, float 0.0, float poison>
   ret <3 x float> %ret
 }
+
+define <2 x float> @mul_pos_zero_neg_value_vec(<2 x float> %a) {
+; CHECK-LABEL: @mul_pos_zero_neg_value_vec(
+; CHECK-NEXT:    [[F2:%.*]] = fmul <2 x float> [[A:%.*]], <float -0.000000e+00, float -0.000000e+00>
+; CHECK-NEXT:    ret <2 x float> [[F2]]
+;
+  %f1 = fmul <2 x float> %a, <float 0.000000, float 0.000000>
+  %f2 = fmul <2 x float> %f1, <float -1.000000, float -1.000000>
+  ret <2 x float> %f2
+}
+
+define <2 x float> @mul_pos_zero_mixed_neg_value_vec(<2 x float> %a) {
+; CHECK-LABEL: @mul_pos_zero_mixed_neg_value_vec(
+; CHECK-NEXT:    [[F2:%.*]] = fmul <2 x float> [[A:%.*]], <float 0.000000e+00, float -0.000000e+00>
+; CHECK-NEXT:    ret <2 x float> [[F2]]
+;
+  %f1 = fmul <2 x float> %a, <float 0.000000, float 0.000000>
+  %f2 = fmul <2 x float> %f1, <float 1.000000, float -1.000000>
+  ret <2 x float> %f2
+}
+
+define <2 x float> @mul_neg_zero_mixed_value_vec(<2 x float> %a) {
+; CHECK-LABEL: @mul_neg_zero_mixed_value_vec(
+; CHECK-NEXT:    [[F2:%.*]] = fmul <2 x float> [[A:%.*]], <float -0.000000e+00, float -0.000000e+00>
+; CHECK-NEXT:    ret <2 x float> [[F2]]
+;
+  %f1 = fmul <2 x float> %a, <float -0.000000, float 0.000000>
+  %f2 = fmul <2 x float> %f1, <float 1.000000, float -1.000000>
+  ret <2 x float> %f2
+}
+
+define float @mul_pos_zero_neg_value(float %a) {
+; CHECK-LABEL: @mul_pos_zero_neg_value(
+; CHECK-NEXT:    [[F2:%.*]] = fmul float [[A:%.*]], -0.000000e+00
+; CHECK-NEXT:    ret float [[F2]]
+;
+  %f1 = fmul float %a, 0.000000
+  %f2 = fmul float %f1, -1.000000
+  ret float %f2
+}
+
+define float @mul_neg_zero_pos_value(float %a) {
+; CHECK-LABEL: @mul_neg_zero_pos_value(
+; CHECK-NEXT:    [[F1:%.*]] = fmul float [[A:%.*]], -0.000000e+00
+; CHECK-NEXT:    ret float [[F1]]
+;
+  %f1 = fmul float %a, -0.000000
+  %f2 = fmul float %f1, 1.000000
+  ret float %f2
+}
+
+define float @mul_neg_zero_neg_value(float %a) {
+; CHECK-LABEL: @mul_neg_zero_neg_value(
+; CHECK-NEXT:    [[F2:%.*]] = fmul float [[A:%.*]], 0.000000e+00
+; CHECK-NEXT:    ret float [[F2]]
+;
+  %f1 = fmul float %a, -0.000000
+  %f2 = fmul float %f1, -1.000000
+  ret float %f2
+}

>From 094ff5586193d6d3c32044784cd585fca6899c3a Mon Sep 17 00:00:00 2001
From: SahilPatidar <patidarsahil2001 at gmail.com>
Date: Sat, 18 May 2024 14:00:15 +0530
Subject: [PATCH 2/2] Fixes code, add and update tests

---
 .../InstCombine/InstCombineMulDivRem.cpp      |  13 +-
 llvm/test/Transforms/InstCombine/fmul.ll      | 147 ++++++++++++++++--
 2 files changed, 142 insertions(+), 18 deletions(-)

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
index 3da1ac909d974..86187c9fcdc89 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
@@ -906,12 +906,13 @@ Instruction *InstCombinerImpl::visitFMul(BinaryOperator &I) {
   }
 
   // (X * 0.0) * constant => X * 0.0
-  if (match(Op0, m_FMul(m_Value(X), m_AnyZeroFP())) &&
-      match(Op1, m_Constant())) {
-    Instruction *FI = cast<Instruction>(Op0);
-    replaceOperand(*FI, 0, Op1);
-    replaceOperand(I, 1, Op0);
-    return replaceOperand(I, 0, X);
+  Constant *C1;
+  if (match(Op0, m_FMul(m_Value(X), m_Constant(C1))) &&
+      match(C1, m_AnyZeroFP()) && match(Op1, m_Constant(C))) {
+    if (Constant *CC1 =
+            ConstantFoldBinaryOpOperands(Instruction::FMul, C, C1, DL)) {
+      return BinaryOperator::CreateFMulFMF(X, CC1, I.getFastMathFlags());
+    }
   }
 
   // Simplify FMUL recurrences starting with 0.0 to 0.0 if nnan and nsz are set.
diff --git a/llvm/test/Transforms/InstCombine/fmul.ll b/llvm/test/Transforms/InstCombine/fmul.ll
index 4ddbbbc622085..564117cb72db5 100644
--- a/llvm/test/Transforms/InstCombine/fmul.ll
+++ b/llvm/test/Transforms/InstCombine/fmul.ll
@@ -1408,8 +1408,8 @@ entry:
   ret <3 x float> %ret
 }
 
-define <2 x float> @mul_pos_zero_neg_value_vec(<2 x float> %a) {
-; CHECK-LABEL: @mul_pos_zero_neg_value_vec(
+define <2 x float> @mul_pos_zero_neg_const_vec(<2 x float> %a) {
+; CHECK-LABEL: @mul_pos_zero_neg_const_vec(
 ; CHECK-NEXT:    [[F2:%.*]] = fmul <2 x float> [[A:%.*]], <float -0.000000e+00, float -0.000000e+00>
 ; CHECK-NEXT:    ret <2 x float> [[F2]]
 ;
@@ -1418,8 +1418,8 @@ define <2 x float> @mul_pos_zero_neg_value_vec(<2 x float> %a) {
   ret <2 x float> %f2
 }
 
-define <2 x float> @mul_pos_zero_mixed_neg_value_vec(<2 x float> %a) {
-; CHECK-LABEL: @mul_pos_zero_mixed_neg_value_vec(
+define <2 x float> @mul_pos_zero_mixed_neg_const_vec(<2 x float> %a) {
+; CHECK-LABEL: @mul_pos_zero_mixed_neg_const_vec(
 ; CHECK-NEXT:    [[F2:%.*]] = fmul <2 x float> [[A:%.*]], <float 0.000000e+00, float -0.000000e+00>
 ; CHECK-NEXT:    ret <2 x float> [[F2]]
 ;
@@ -1428,8 +1428,8 @@ define <2 x float> @mul_pos_zero_mixed_neg_value_vec(<2 x float> %a) {
   ret <2 x float> %f2
 }
 
-define <2 x float> @mul_neg_zero_mixed_value_vec(<2 x float> %a) {
-; CHECK-LABEL: @mul_neg_zero_mixed_value_vec(
+define <2 x float> @mul_neg_zero_mixed_const_vec(<2 x float> %a) {
+; CHECK-LABEL: @mul_neg_zero_mixed_const_vec(
 ; CHECK-NEXT:    [[F2:%.*]] = fmul <2 x float> [[A:%.*]], <float -0.000000e+00, float -0.000000e+00>
 ; CHECK-NEXT:    ret <2 x float> [[F2]]
 ;
@@ -1438,8 +1438,29 @@ define <2 x float> @mul_neg_zero_mixed_value_vec(<2 x float> %a) {
   ret <2 x float> %f2
 }
 
-define float @mul_pos_zero_neg_value(float %a) {
-; CHECK-LABEL: @mul_pos_zero_neg_value(
+define <2 x float> @mul_neg_zero_mixed_const_vec_ninf(<2 x float> %a) {
+; CHECK-LABEL: @mul_neg_zero_mixed_const_vec_ninf(
+; CHECK-NEXT:    [[F2:%.*]] = fmul ninf <2 x float> [[A:%.*]], <float -0.000000e+00, float -0.000000e+00>
+; CHECK-NEXT:    ret <2 x float> [[F2]]
+;
+  %f1 = fmul ninf <2 x float> %a, <float -0.000000, float 0.000000>
+  %f2 = fmul ninf <2 x float> %f1, <float 1.000000, float -1.000000>
+  ret <2 x float> %f2
+}
+
+define <2 x float> @mul_neg_zero_mixed_const_vec_nnan(<2 x float> %a) {
+; CHECK-LABEL: @mul_neg_zero_mixed_const_vec_nnan(
+; CHECK-NEXT:    [[TMP1:%.*]] = fneg nnan <2 x float> [[A:%.*]]
+; CHECK-NEXT:    [[F2:%.*]] = call nnan <2 x float> @llvm.copysign.v2f32(<2 x float> zeroinitializer, <2 x float> [[TMP1]])
+; CHECK-NEXT:    ret <2 x float> [[F2]]
+;
+  %f1 = fmul nnan <2 x float> %a, <float -0.000000, float 0.000000>
+  %f2 = fmul nnan <2 x float> %f1, <float 1.000000, float -1.000000>
+  ret <2 x float> %f2
+}
+
+define float @mul_pos_zero_neg_const(float %a) {
+; CHECK-LABEL: @mul_pos_zero_neg_const(
 ; CHECK-NEXT:    [[F2:%.*]] = fmul float [[A:%.*]], -0.000000e+00
 ; CHECK-NEXT:    ret float [[F2]]
 ;
@@ -1448,8 +1469,8 @@ define float @mul_pos_zero_neg_value(float %a) {
   ret float %f2
 }
 
-define float @mul_neg_zero_pos_value(float %a) {
-; CHECK-LABEL: @mul_neg_zero_pos_value(
+define float @mul_neg_zero_pos_const(float %a) {
+; CHECK-LABEL: @mul_neg_zero_pos_const(
 ; CHECK-NEXT:    [[F1:%.*]] = fmul float [[A:%.*]], -0.000000e+00
 ; CHECK-NEXT:    ret float [[F1]]
 ;
@@ -1458,8 +1479,8 @@ define float @mul_neg_zero_pos_value(float %a) {
   ret float %f2
 }
 
-define float @mul_neg_zero_neg_value(float %a) {
-; CHECK-LABEL: @mul_neg_zero_neg_value(
+define float @mul_neg_zero_neg_const(float %a) {
+; CHECK-LABEL: @mul_neg_zero_neg_const(
 ; CHECK-NEXT:    [[F2:%.*]] = fmul float [[A:%.*]], 0.000000e+00
 ; CHECK-NEXT:    ret float [[F2]]
 ;
@@ -1467,3 +1488,105 @@ define float @mul_neg_zero_neg_value(float %a) {
   %f2 = fmul float %f1, -1.000000
   ret float %f2
 }
+
+define float @mul_neg_zero_pos_const_ninf(float %a) {
+; CHECK-LABEL: @mul_neg_zero_pos_const_ninf(
+; CHECK-NEXT:    [[F1:%.*]] = fmul ninf float [[A:%.*]], -0.000000e+00
+; CHECK-NEXT:    ret float [[F1]]
+;
+  %f1 = fmul ninf float %a, -0.000000
+  %f2 = fmul ninf float %f1, 1.000000
+  ret float %f2
+}
+
+define float @mul_neg_zero_neg_const_ninf(float %a) {
+; CHECK-LABEL: @mul_neg_zero_neg_const_ninf(
+; CHECK-NEXT:    [[F2:%.*]] = fmul ninf float [[A:%.*]], 0.000000e+00
+; CHECK-NEXT:    ret float [[F2]]
+;
+  %f1 = fmul ninf float %a, -0.000000
+  %f2 = fmul ninf float %f1, -1.000000
+  ret float %f2
+}
+
+define float @mul_pos_zero_neg_const_ninf(float %a) {
+; CHECK-LABEL: @mul_pos_zero_neg_const_ninf(
+; CHECK-NEXT:    [[F2:%.*]] = fmul ninf float [[A:%.*]], -0.000000e+00
+; CHECK-NEXT:    ret float [[F2]]
+;
+  %f1 = fmul ninf float %a, 0.000000
+  %f2 = fmul ninf float %f1, -1.000000
+  ret float %f2
+}
+
+define float @mul_neg_zero_pos_const_nnan(float %a) {
+; CHECK-LABEL: @mul_neg_zero_pos_const_nnan(
+; CHECK-NEXT:    [[TMP1:%.*]] = fneg nnan float [[A:%.*]]
+; CHECK-NEXT:    [[F1:%.*]] = call nnan float @llvm.copysign.f32(float 0.000000e+00, float [[TMP1]])
+; CHECK-NEXT:    ret float [[F1]]
+;
+  %f1 = fmul nnan float %a, -0.000000
+  %f2 = fmul nnan float %f1, 1.000000
+  ret float %f2
+}
+
+define float @mul_neg_zero_neg_const_nnan(float %a) {
+; CHECK-LABEL: @mul_neg_zero_neg_const_nnan(
+; CHECK-NEXT:    [[F2:%.*]] = call nnan float @llvm.copysign.f32(float 0.000000e+00, float [[A:%.*]])
+; CHECK-NEXT:    ret float [[F2]]
+;
+  %f1 = fmul nnan float %a, -0.000000
+  %f2 = fmul nnan float %f1, -1.000000
+  ret float %f2
+}
+
+define float @mul_pos_zero_neg_const_nnan(float %a) {
+; CHECK-LABEL: @mul_pos_zero_neg_const_nnan(
+; CHECK-NEXT:    [[TMP1:%.*]] = fneg nnan float [[A:%.*]]
+; CHECK-NEXT:    [[F2:%.*]] = call nnan float @llvm.copysign.f32(float 0.000000e+00, float [[TMP1]])
+; CHECK-NEXT:    ret float [[F2]]
+;
+  %f1 = fmul nnan float %a, 0.000000
+  %f2 = fmul nnan float %f1, -1.000000
+  ret float %f2
+}
+
+define float @mul_neg_zero_const_expr(float %a) {
+; CHECK-LABEL: @mul_neg_zero_const_expr(
+; CHECK-NEXT:    [[F3:%.*]] = fmul float [[A:%.*]], -0.000000e+00
+; CHECK-NEXT:    ret float [[F3]]
+;
+  %f1 = fmul float %a, -0.000000e+00
+  %i1 = inttoptr i32 1000 to ptr
+  %i = ptrtoint ptr %i1 to i32
+  %f2 = bitcast i32 %i to float
+  %f3 = fmul float %f1, %f2
+  ret float %f3
+}
+
+define float @mul_neg_zero_expr(float %a, ptr %b) {
+; CHECK-LABEL: @mul_neg_zero_expr(
+; CHECK-NEXT:    [[F1:%.*]] = fmul float [[A:%.*]], -0.000000e+00
+; CHECK-NEXT:    [[TMP1:%.*]] = ptrtoint ptr [[B:%.*]] to i64
+; CHECK-NEXT:    [[I:%.*]] = trunc i64 [[TMP1]] to i32
+; CHECK-NEXT:    [[F2:%.*]] = bitcast i32 [[I]] to float
+; CHECK-NEXT:    [[F3:%.*]] = fmul float [[F1]], [[F2]]
+; CHECK-NEXT:    ret float [[F3]]
+;
+  %f1 = fmul float %a, -0.000000e+00
+  %i = ptrtoint ptr %b to i32
+  %f2 = bitcast i32 %i to float
+  %f3 = fmul float %f1, %f2
+  ret float %f3
+}
+
+define float @mul_neg_zero_expr2(float %a, ptr %b) {
+; CHECK-LABEL: @mul_neg_zero_expr2(
+; CHECK-NEXT:    [[F1:%.*]] = fmul float [[A:%.*]], -0.000000e+00
+; CHECK-NEXT:    [[F2:%.*]] = fmul float [[F1]], bitcast (i32 ptrtoint (ptr getelementptr inbounds ({ [2 x ptr] }, ptr @g, i64 1, i32 0, i64 0) to i32) to float)
+; CHECK-NEXT:    ret float [[F2]]
+;
+  %f1 = fmul float %a, -0.000000e+00
+  %f2 = fmul float %f1, bitcast (i32 ptrtoint (ptr getelementptr inbounds ({ [2 x ptr] }, ptr @g, i64 0, i32 0, i64 2) to i32) to float)
+  ret float %f2
+}



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