Author: nicholas
Date: Mon Jan 21 23:08:48 2008
New Revision: 46244
URL: http://llvm.org/viewvc/llvm-project?rev=46244&view=rev
Log:
Multiply can be evaluated in a different type, so long as the target type has
a smaller bitwidth.
Added:
llvm/trunk/test/Transforms/InstCombine/2008-01-21-MulTrunc.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=46244&r1=46243&r2=46244&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp Mon Jan 21
23:08:48 2008
@@ -6512,6 +6512,15 @@
CanEvaluateInDifferentType(I->getOperand(1), Ty, CastOpc,
NumCastsRemoved);
+ case Instruction::Mul:
+ break;
+ // A multiply can be truncated by truncating its operands.
+ return Ty->getBitWidth() < OrigTy->getBitWidth() &&
+ CanEvaluateInDifferentType(I->getOperand(0), Ty, CastOpc,
+ NumCastsRemoved) &&
+ CanEvaluateInDifferentType(I->getOperand(1), Ty, CastOpc,
+ NumCastsRemoved);
+
case Instruction::Shl:
// If we are truncating the result of this SHL, and if it's a shift of a
// constant amount, we can always perform a SHL in a smaller type.
@@ -6571,6 +6580,7 @@
switch (I->getOpcode()) {
case Instruction::Add:
case Instruction::Sub:
+ case Instruction::Mul:
case Instruction::And:
case Instruction::Or:
case Instruction::Xor:
Added: llvm/trunk/test/Transforms/InstCombine/2008-01-21-MulTrunc.ll
URL:
http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/2008-01-21-MulTrunc.ll?rev=46244&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/2008-01-21-MulTrunc.ll (added)
+++ llvm/trunk/test/Transforms/InstCombine/2008-01-21-MulTrunc.ll Mon Jan 21
23:08:48 2008
@@ -0,0 +1,11 @@
+; RUN: llvm-as < %s | opt -instcombine | llvm-dis | notcast
+
+define i16 @test1(i16 %a) {
+ %tmp = zext i16 %a to i32 ; <i32> [#uses=2]
+ %tmp21 = lshr i32 %tmp, 8 ; <i32> [#uses=1]
+ %tmp5 = mul i32 %tmp, 5 ; <i32> [#uses=1]
+ %tmp.upgrd.32 = or i32 %tmp21, %tmp5 ; <i32> [#uses=1]
+ %tmp.upgrd.3 = trunc i32 %tmp.upgrd.32 to i16 ; <i16>
[#uses=1]
+ ret i16 %tmp.upgrd.3
+}
+
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