[llvm-commits] [llvm] r94318 - in /llvm/trunk: lib/Target/README.txt lib/Transforms/InstCombine/InstCombineShifts.cpp test/Transforms/InstCombine/intrinsics.ll
Chris Lattner
sabre at nondot.org
Sat Jan 23 10:49:31 PST 2010
Author: lattner
Date: Sat Jan 23 12:49:30 2010
New Revision: 94318
URL: http://llvm.org/viewvc/llvm-project?rev=94318&view=rev
Log:
implement a simple instcombine xform that has been in the
readme forever.
Modified:
llvm/trunk/lib/Target/README.txt
llvm/trunk/lib/Transforms/InstCombine/InstCombineShifts.cpp
llvm/trunk/test/Transforms/InstCombine/intrinsics.ll
Modified: llvm/trunk/lib/Target/README.txt
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/README.txt?rev=94318&r1=94317&r2=94318&view=diff
==============================================================================
--- llvm/trunk/lib/Target/README.txt (original)
+++ llvm/trunk/lib/Target/README.txt Sat Jan 23 12:49:30 2010
@@ -237,24 +237,6 @@
//===---------------------------------------------------------------------===//
-dag/inst combine "clz(x)>>5 -> x==0" for 32-bit x.
-
-Compile:
-
-int bar(int x)
-{
- int t = __builtin_clz(x);
- return -(t>>5);
-}
-
-to:
-
-_bar: addic r3,r3,-1
- subfe r3,r3,r3
- blr
-
-//===---------------------------------------------------------------------===//
-
quantum_sigma_x in 462.libquantum contains the following loop:
for(i=0; i<reg->size; i++)
@@ -294,6 +276,8 @@
//===---------------------------------------------------------------------===//
+[LOOP RECOGNITION]
+
These idioms should be recognized as popcount (see PR1488):
unsigned countbits_slow(unsigned v) {
Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineShifts.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineShifts.cpp?rev=94318&r1=94317&r2=94318&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineShifts.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineShifts.cpp Sat Jan 23 12:49:30 2010
@@ -12,6 +12,7 @@
//===----------------------------------------------------------------------===//
#include "InstCombine.h"
+#include "llvm/IntrinsicInst.h"
#include "llvm/Support/PatternMatch.h"
using namespace llvm;
using namespace PatternMatch;
@@ -69,10 +70,9 @@
if (Op1->uge(TypeBits)) {
if (I.getOpcode() != Instruction::AShr)
return ReplaceInstUsesWith(I, Constant::getNullValue(Op0->getType()));
- else {
- I.setOperand(1, ConstantInt::get(I.getType(), TypeBits-1));
- return &I;
- }
+ // ashr i32 X, 32 --> ashr i32 X, 31
+ I.setOperand(1, ConstantInt::get(I.getType(), TypeBits-1));
+ return &I;
}
// ((X*C1) << C2) == (X * (C1 << C2))
@@ -387,7 +387,29 @@
}
Instruction *InstCombiner::visitLShr(BinaryOperator &I) {
- return commonShiftTransforms(I);
+ if (Instruction *R = commonShiftTransforms(I))
+ return R;
+
+ Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
+
+ if (ConstantInt *Op1C = dyn_cast<ConstantInt>(Op1))
+ if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Op0)) {
+ // ctlz.i32(x)>>5 --> zext(x == 0)
+ // cttz.i32(x)>>5 --> zext(x == 0)
+ // ctpop.i32(x)>>5 --> zext(x == -1)
+ if ((II->getIntrinsicID() == Intrinsic::ctlz ||
+ II->getIntrinsicID() == Intrinsic::cttz ||
+ II->getIntrinsicID() == Intrinsic::ctpop) &&
+ (1ULL << Op1C->getZExtValue()) ==
+ Op0->getType()->getScalarSizeInBits()) {
+ bool isCtPop = II->getIntrinsicID() == Intrinsic::ctpop;
+ Constant *RHS = ConstantInt::getSigned(Op0->getType(), isCtPop ? -1 : 0);
+ Value *Cmp = Builder->CreateICmpEQ(II->getOperand(1), RHS);
+ return new ZExtInst(Cmp, II->getType());
+ }
+ }
+
+ return 0;
}
Instruction *InstCombiner::visitAShr(BinaryOperator &I) {
Modified: llvm/trunk/test/Transforms/InstCombine/intrinsics.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/intrinsics.ll?rev=94318&r1=94317&r2=94318&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/intrinsics.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/intrinsics.ll Sat Jan 23 12:49:30 2010
@@ -144,3 +144,18 @@
; CHECK-NEXT: %pop.cmp = icmp eq i32 %b, 0
; CHECK-NEXT: volatile store i1 %pop.cmp, i1* %c
}
+
+
+define i32 @cttz_simplify1(i32 %x) nounwind readnone ssp {
+ %tmp1 = tail call i32 @llvm.ctlz.i32(i32 %x) ; <i32> [#uses=1]
+ %shr3 = lshr i32 %tmp1, 5 ; <i32> [#uses=1]
+ ret i32 %shr3
+
+; CHECK: @cttz_simplify1
+; CHECK: icmp eq i32 %x, 0
+; CHECK-NEXT: zext i1
+; CHECK-NEXT: ret i32
+}
+
+declare i32 @llvm.ctlz.i32(i32) nounwind readnone
+
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