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Similarly, analyze truncate through multiply.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@123842 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Nick Lewycky 2011-01-19 18:56:00 +00:00
parent 30aa8b13c9
commit 5c6fc1cab7
2 changed files with 22 additions and 0 deletions
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14
lib/Analysis/ScalarEvolution.cpp
View File

@ -833,6 +833,20 @@ const SCEV *ScalarEvolution::getTruncateExpr(const SCEV *Op,
return getAddExpr(Operands, false, false);
}
// trunc(x1*x2*...*xN) --> trunc(x1)*trunc(x2)*...*trunc(xN) if we can
// eliminate all the truncates.
if (const SCEVMulExpr *SM = dyn_cast<SCEVMulExpr>(Op)) {
SmallVector<const SCEV *, 4> Operands;
bool hasTrunc = false;
for (unsigned i = 0, e = SM->getNumOperands(); i != e && !hasTrunc; ++i) {
const SCEV *S = getTruncateExpr(SM->getOperand(i), Ty);
hasTrunc = isa<SCEVTruncateExpr>(S);
Operands.push_back(S);
}
if (!hasTrunc)
return getMulExpr(Operands, false, false);
}
// If the input value is a chrec scev, truncate the chrec's operands.
if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(Op)) {
SmallVector<const SCEV *, 4> Operands;

8
test/Analysis/ScalarEvolution/fold.ll
View File

@ -14,3 +14,11 @@ define i8 @test2(i8 %x) {
; CHECK: (1 + %x)
ret i8 %C
}
define i8 @test3(i8 %x) {
%A = zext i8 %x to i16
%B = mul i16 %A, 1027
%C = trunc i16 %B to i8
; CHECK: (3 * %x)
ret i8 %C
}