[llvm-commits] [llvm] r78714 - in /llvm/trunk: lib/Transforms/Scalar/InstructionCombining.cpp test/Transforms/InstCombine/exact-sdiv.ll
Dan Gohman
gohman at apple.com
Tue Aug 11 13:47:47 PDT 2009
Author: djg
Date: Tue Aug 11 15:47:47 2009
New Revision: 78714
URL: http://llvm.org/viewvc/llvm-project?rev=78714&view=rev
Log:
Optimize exact sdiv by a constant power of 2 to ashr.
Added:
llvm/trunk/test/Transforms/InstCombine/exact-sdiv.ll
Modified:
llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp
Modified: llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp?rev=78714&r1=78713&r2=78714&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp Tue Aug 11 15:47:47 2009
@@ -3064,6 +3064,15 @@
// sdiv X, -1 == -X
if (RHS->isAllOnesValue())
return BinaryOperator::CreateNeg(*Context, Op0);
+
+ // sdiv X, C --> ashr X, log2(C)
+ if (cast<SDivOperator>(&I)->isExact() &&
+ RHS->getValue().isNonNegative() &&
+ RHS->getValue().isPowerOf2()) {
+ Value *ShAmt = llvm::ConstantInt::get(RHS->getType(),
+ RHS->getValue().exactLogBase2());
+ return BinaryOperator::CreateAShr(Op0, ShAmt, I.getName());
+ }
}
// If the sign bits of both operands are zero (i.e. we can prove they are
Added: llvm/trunk/test/Transforms/InstCombine/exact-sdiv.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/exact-sdiv.ll?rev=78714&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/exact-sdiv.ll (added)
+++ llvm/trunk/test/Transforms/InstCombine/exact-sdiv.ll Tue Aug 11 15:47:47 2009
@@ -0,0 +1,15 @@
+; RUN: llvm-as < %s | opt -instcombine | llvm-dis | FileCheck %s
+
+; CHECK: define i32 @foo
+; CHECK: sdiv i32 %x, 8
+define i32 @foo(i32 %x) {
+ %y = sdiv i32 %x, 8
+ ret i32 %y
+}
+
+; CHECK: define i32 @bar
+; CHECK: ashr i32 %x, 3
+define i32 @bar(i32 %x) {
+ %y = sdiv exact i32 %x, 8
+ ret i32 %y
+}
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