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SimplifyCFG: GEPs with just one non-constant index are also cheap.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@126452 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Benjamin Kramer 2011-02-24 23:26:09 +00:00
parent 107d366df7
commit 9ae59e3444
2 changed files with 27 additions and 5 deletions
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8
lib/Transforms/Utils/SimplifyCFG.cpp
View File

@ -247,11 +247,13 @@ static bool DominatesMergePoint(Value *V, BasicBlock *BB,
if (PBB->getFirstNonPHIOrDbg() != I)
return false;
break;
case Instruction::GetElementPtr:
// GEPs are cheap if all indices are constant.
if (!cast<GetElementPtrInst>(I)->hasAllConstantIndices())
case Instruction::GetElementPtr: {
// GEPs are cheap if all indices are constant or if there's only one index.
GetElementPtrInst *GEP = cast<GetElementPtrInst>(I);
if (!GEP->hasAllConstantIndices() && GEP->getNumIndices() > 1)
return false;
break;
}
case Instruction::Add:
case Instruction::Sub:
case Instruction::And:

24
test/Transforms/SimplifyCFG/select-gep.ll
View File

@ -1,13 +1,13 @@
; RUN: opt -S -simplifycfg %s | FileCheck %s
define i8* @test1(i8* %x) nounwind {
define i8* @test1(i8* %x, i64 %y) nounwind {
entry:
%tmp1 = load i8* %x, align 1
%cmp = icmp eq i8 %tmp1, 47
br i1 %cmp, label %if.then, label %if.end
if.then:
%incdec.ptr = getelementptr inbounds i8* %x, i64 1
%incdec.ptr = getelementptr inbounds i8* %x, i64 %y
br label %if.end
if.end:
@ -18,3 +18,23 @@ if.end:
; CHECK: %x.addr = select i1 %cmp, i8* %incdec.ptr, i8* %x
; CHECK: ret i8* %x.addr
}
%ST = type { i8, i8 }
define i8* @test2(%ST* %x, i8* %y) nounwind {
entry:
%cmp = icmp eq %ST* %x, null
br i1 %cmp, label %if.then, label %if.end
if.then:
%incdec.ptr = getelementptr %ST* %x, i32 0, i32 1
br label %if.end
if.end:
%x.addr = phi i8* [ %incdec.ptr, %if.then ], [ %y, %entry ]
ret i8* %x.addr
; CHECK: @test2
; CHECK: %x.addr = select i1 %cmp, i8* %incdec.ptr, i8* %y
; CHECK: ret i8* %x.addr
}