[PATCH] D67553: [InstSimplify] Match 1.0 and 0.0 for both operands in SimplifyFMAMul

[Florian Hahn via Phabricator via llvm-commits]

fhahn created this revision.
fhahn added reviewers: lebedev.ri, spatel, reames, scanon.
Herald added a subscriber: hiraditya.
Herald added a project: LLVM.

Because we do not constant fold multiplications in SimplifyFMAMul,
we match 1.0 and 0.0 for both operands, as multiplying by them
is guaranteed to produce an exact result (if it is allowed to do so).

Note that it is not enough to just swap the operands to ensure a
constant is on the RHS, as we want to also cover the case with
2 constants.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D67553

Files:
  llvm/lib/Analysis/InstructionSimplify.cpp
  llvm/test/Transforms/InstCombine/fma.ll


Index: llvm/test/Transforms/InstCombine/fma.ll
===================================================================
--- llvm/test/Transforms/InstCombine/fma.ll
+++ llvm/test/Transforms/InstCombine/fma.ll
@@ -460,8 +460,7 @@
 define <2 x double> @fma_const_fmul_zero(<2 x double> %b) {
 ; CHECK-LABEL: @fma_const_fmul_zero(
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    [[RES:%.*]] = call nnan nsz <2 x double> @llvm.fma.v2f64(<2 x double> zeroinitializer, <2 x double> <double 0x4131233302898702, double 0x40C387800000D6C0>, <2 x double> [[B:%.*]])
-; CHECK-NEXT:    ret <2 x double> [[RES]]
+; CHECK-NEXT:    ret <2 x double> [[B:%.*]]
 ;
 entry:
   %res = call nnan nsz <2 x double> @llvm.fma.v2f64(<2 x double> <double 0.0, double 0.0>, <2 x double> <double 1123123.0099110012314, double 9999.0000001>, <2 x double> %b)
@@ -481,7 +480,7 @@
 define <2 x double> @fma_const_fmul_one(<2 x double> %b) {
 ; CHECK-LABEL: @fma_const_fmul_one(
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    [[RES:%.*]] = call nnan nsz <2 x double> @llvm.fma.v2f64(<2 x double> <double 1.000000e+00, double 1.000000e+00>, <2 x double> <double 0x4131233302898702, double 0x40C387800000D6C0>, <2 x double> [[B:%.*]])
+; CHECK-NEXT:    [[RES:%.*]] = fadd nnan nsz <2 x double> [[B:%.*]], <double 0x4131233302898702, double 0x40C387800000D6C0>
 ; CHECK-NEXT:    ret <2 x double> [[RES]]
 ;
 entry:
Index: llvm/lib/Analysis/InstructionSimplify.cpp
===================================================================
--- llvm/lib/Analysis/InstructionSimplify.cpp
+++ llvm/lib/Analysis/InstructionSimplify.cpp
@@ -4562,10 +4562,18 @@
   if (match(Op1, m_FPOne()))
     return Op0;
 
+  // fmul 1.0, X ==> X
+  if (match(Op0, m_FPOne()))
+    return Op1;
+
   // fmul nnan nsz X, 0 ==> 0
   if (FMF.noNaNs() && FMF.noSignedZeros() && match(Op1, m_AnyZeroFP()))
     return ConstantFP::getNullValue(Op0->getType());
 
+  // fmul nnan nsz 0, X ==> 0
+  if (FMF.noNaNs() && FMF.noSignedZeros() && match(Op0, m_AnyZeroFP()))
+    return ConstantFP::getNullValue(Op1->getType());
+
   // sqrt(X) * sqrt(X) --> X, if we can:
   // 1. Remove the intermediate rounding (reassociate).
   // 2. Ignore non-zero negative numbers because sqrt would produce NAN.


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