[llvm] 10cb23c - [InstCombine] Fold cttz of abs intrinsic

[Nikita Popov via llvm-commits]

Author: Nikita Popov
Date: 2020-09-05T12:25:41+02:00
New Revision: 10cb23c6ca451374ebe2f31add236692e01637f3

URL: https://github.com/llvm/llvm-project/commit/10cb23c6ca451374ebe2f31add236692e01637f3
DIFF: https://github.com/llvm/llvm-project/commit/10cb23c6ca451374ebe2f31add236692e01637f3.diff

LOG: [InstCombine] Fold cttz of abs intrinsic

Same as the existing fold for SPF_ABS. We don't need to explicitly
handle the NABS variant, as we'll first fold away the neg in that
case.

Added: 
    

Modified: 
    llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
    llvm/test/Transforms/InstCombine/cttz-abs.ll

Removed: 
    


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diff  --git a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
index dd4e48170f02..311a18c7f584 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -428,6 +428,9 @@ static Instruction *foldCttzCtlz(IntrinsicInst &II, InstCombinerImpl &IC) {
     SelectPatternFlavor SPF = matchSelectPattern(Op0, X, Y).Flavor;
     if (SPF == SPF_ABS || SPF == SPF_NABS)
       return IC.replaceOperand(II, 0, X);
+
+    if (match(Op0, m_Intrinsic<Intrinsic::abs>(m_Value(X))))
+      return IC.replaceOperand(II, 0, X);
   }
 
   KnownBits Known = IC.computeKnownBits(Op0, 0, &II);

diff  --git a/llvm/test/Transforms/InstCombine/cttz-abs.ll b/llvm/test/Transforms/InstCombine/cttz-abs.ll
index 8da3668997fa..b89a55c8f5b8 100644
--- a/llvm/test/Transforms/InstCombine/cttz-abs.ll
+++ b/llvm/test/Transforms/InstCombine/cttz-abs.ll
@@ -218,8 +218,7 @@ define <2 x i64> @no_cttz_nabs_vec(<2 x i64> %x) {
 
 define i32 @cttz_abs_intrin(i32 %x) {
 ; CHECK-LABEL: @cttz_abs_intrin(
-; CHECK-NEXT:    [[A:%.*]] = call i32 @llvm.abs.i32(i32 [[X:%.*]], i1 false)
-; CHECK-NEXT:    [[R:%.*]] = call i32 @llvm.cttz.i32(i32 [[A]], i1 false), [[RNG0]]
+; CHECK-NEXT:    [[R:%.*]] = call i32 @llvm.cttz.i32(i32 [[X:%.*]], i1 false), [[RNG0]]
 ; CHECK-NEXT:    ret i32 [[R]]
 ;
   %a = call i32 @llvm.abs.i32(i32 %x, i1 false)
@@ -229,8 +228,7 @@ define i32 @cttz_abs_intrin(i32 %x) {
 
 define i32 @cttz_nabs_intrin(i32 %x) {
 ; CHECK-LABEL: @cttz_nabs_intrin(
-; CHECK-NEXT:    [[A:%.*]] = call i32 @llvm.abs.i32(i32 [[X:%.*]], i1 false)
-; CHECK-NEXT:    [[R:%.*]] = call i32 @llvm.cttz.i32(i32 [[A]], i1 false), [[RNG0]]
+; CHECK-NEXT:    [[R:%.*]] = call i32 @llvm.cttz.i32(i32 [[X:%.*]], i1 false), [[RNG0]]
 ; CHECK-NEXT:    ret i32 [[R]]
 ;
   %a = call i32 @llvm.abs.i32(i32 %x, i1 false)