[PATCH] D79321: [SLC] Allow llvm.pow(2**n,x) -> llvm.exp2(n*x) even if no exp2 lib func

[Jay Foad via Phabricator via llvm-commits]

foad created this revision.
foad added reviewers: evandro, efriedma, spatel, lebedev.ri.
Herald added subscribers: llvm-commits, hiraditya.
Herald added a project: LLVM.

replacePowWithExp generates a call either to the llvm.exp2 intrinsic or
to the exp2 library function. Allow it to use the intrinsic even if the
library function is not available.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D79321

Files:
  llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
  llvm/test/Transforms/InstCombine/pow-1.ll


Index: llvm/test/Transforms/InstCombine/pow-1.ll
===================================================================
--- llvm/test/Transforms/InstCombine/pow-1.ll
+++ llvm/test/Transforms/InstCombine/pow-1.ll
@@ -107,13 +107,8 @@
 
 define <2 x float> @test_simplify3v(<2 x float> %x) {
 ; CHECK-LABEL: @test_simplify3v(
-; ANY-NEXT:    [[EXP2:%.*]] = call <2 x float> @llvm.exp2.v2f32(<2 x float> [[X:%.*]])
-; ANY-NEXT:    ret <2 x float> [[EXP2]]
-; MSVC-NEXT:   [[POW:%.*]] = call <2 x float> @llvm.pow.v2f32(<2 x float> <float 2.000000e+00, float 2.000000e+00>, <2 x float> [[X:%.*]])
-; MSVC-NEXT:   ret <2 x float> [[POW]]
-; TODO: should be able to simplify llvm.pow to llvm.exp2 even without libcalls
-; NOLIB-NEXT:    [[POW:%.*]] = call <2 x float> @llvm.pow.v2f32(<2 x float> <float 2.000000e+00, float 2.000000e+00>, <2 x float> [[X:%.*]])
-; NOLIB-NEXT:    ret <2 x float> [[POW]]
+; CHECK-NEXT:    [[EXP2:%.*]] = call <2 x float> @llvm.exp2.v2f32(<2 x float> [[X:%.*]])
+; CHECK-NEXT:    ret <2 x float> [[EXP2]]
 ;
   %retval = call <2 x float> @llvm.pow.v2f32(<2 x float> <float 2.0, float 2.0>, <2 x float> %x)
   ret <2 x float> %retval
@@ -121,14 +116,9 @@
 
 define <2 x double> @test_simplify3vn(<2 x double> %x) {
 ; CHECK-LABEL: @test_simplify3vn(
-; ANY-NEXT:    [[MUL:%.*]] = fmul <2 x double> [[X:%.*]], <double 2.000000e+00, double 2.000000e+00>
-; ANY-NEXT:    [[EXP2:%.*]] = call <2 x double> @llvm.exp2.v2f64(<2 x double> [[MUL]])
-; ANY-NEXT:    ret <2 x double> [[EXP2]]
-; MSVC-NEXT:   [[POW:%.*]] = call <2 x double> @llvm.pow.v2f64(<2 x double> <double 4.000000e+00, double 4.000000e+00>, <2 x double> [[X:%.*]])
-; MSVC-NEXT:   ret <2 x double> [[POW]]
-; TODO: should be able to simplify llvm.pow to llvm.exp2 even without libcalls
-; NOLIB-NEXT:    [[POW:%.*]] = call <2 x double> @llvm.pow.v2f64(<2 x double> <double 4.000000e+00, double 4.000000e+00>, <2 x double> [[X:%.*]])
-; NOLIB-NEXT:    ret <2 x double> [[POW]]
+; CHECK-NEXT:    [[MUL:%.*]] = fmul <2 x double> [[X:%.*]], <double 2.000000e+00, double 2.000000e+00>
+; CHECK-NEXT:    [[EXP2:%.*]] = call <2 x double> @llvm.exp2.v2f64(<2 x double> [[MUL]])
+; CHECK-NEXT:    ret <2 x double> [[EXP2]]
 ;
   %retval = call <2 x double> @llvm.pow.v2f64(<2 x double> <double 4.0, double 4.0>, <2 x double> %x)
   ret <2 x double> %retval
@@ -174,13 +164,8 @@
 
 define <2 x double> @test_simplify4v(<2 x double> %x) {
 ; CHECK-LABEL: @test_simplify4v(
-; ANY-NEXT:    [[EXP2:%.*]] = call <2 x double> @llvm.exp2.v2f64(<2 x double> [[X:%.*]])
-; ANY-NEXT:    ret <2 x double> [[EXP2]]
-; MSVC-NEXT:   [[POW:%.*]] = call <2 x double> @llvm.pow.v2f64(<2 x double> <double 2.000000e+00, double 2.000000e+00>, <2 x double> [[X:%.*]])
-; MSVC-NEXT:   ret <2 x double> [[POW]]
-; TODO: should be able to simplify llvm.pow to llvm.exp2 even without libcalls
-; NOLIB-NEXT:    [[POW:%.*]] = call <2 x double> @llvm.pow.v2f64(<2 x double> <double 2.000000e+00, double 2.000000e+00>, <2 x double> [[X:%.*]])
-; NOLIB-NEXT:    ret <2 x double> [[POW]]
+; CHECK-NEXT:    [[EXP2:%.*]] = call <2 x double> @llvm.exp2.v2f64(<2 x double> [[X:%.*]])
+; CHECK-NEXT:    ret <2 x double> [[EXP2]]
 ;
   %retval = call <2 x double> @llvm.pow.v2f64(<2 x double> <double 2.0, double 2.0>, <2 x double> %x)
   ret <2 x double> %retval
@@ -188,14 +173,9 @@
 
 define <2 x float> @test_simplify4vn(<2 x float> %x) {
 ; CHECK-LABEL: @test_simplify4vn(
-; ANY-NEXT:    [[MUL:%.*]] = fneg <2 x float> [[X:%.*]]
-; ANY-NEXT:    [[EXP2:%.*]] = call <2 x float> @llvm.exp2.v2f32(<2 x float> [[MUL]])
-; ANY-NEXT:    ret <2 x float> [[EXP2]]
-; MSVC-NEXT:   [[POW:%.*]] = call <2 x float> @llvm.pow.v2f32(<2 x float> <float 5.000000e-01, float 5.000000e-01>, <2 x float> [[X:%.*]])
-; MSVC-NEXT:   ret <2 x float> [[POW]]
-; TODO: should be able to simplify llvm.pow to llvm.exp2 even without libcalls
-; NOLIB-NEXT:    [[POW:%.*]] = call <2 x float> @llvm.pow.v2f32(<2 x float> <float 5.000000e-01, float 5.000000e-01>, <2 x float> [[X:%.*]])
-; NOLIB-NEXT:    ret <2 x float> [[POW]]
+; CHECK-NEXT:    [[MUL:%.*]] = fneg <2 x float> [[X:%.*]]
+; CHECK-NEXT:    [[EXP2:%.*]] = call <2 x float> @llvm.exp2.v2f32(<2 x float> [[MUL]])
+; CHECK-NEXT:    ret <2 x float> [[EXP2]]
 ;
   %retval = call <2 x float> @llvm.pow.v2f32(<2 x float> <float 0.5, float 0.5>, <2 x float> %x)
   ret <2 x float> %retval
Index: llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
===================================================================
--- llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
+++ llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
@@ -1534,7 +1534,8 @@
   }
 
   // pow(2.0 ** n, x) -> exp2(n * x)
-  if (hasFloatFn(TLI, Ty, LibFunc_exp2, LibFunc_exp2f, LibFunc_exp2l)) {
+  if (Pow->doesNotAccessMemory() ||
+      hasFloatFn(TLI, Ty, LibFunc_exp2, LibFunc_exp2f, LibFunc_exp2l)) {
     APFloat BaseR = APFloat(1.0);
     BaseR.convert(BaseF->getSemantics(), APFloat::rmTowardZero, &Ignored);
     BaseR = BaseR / *BaseF;


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