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Tail duplication still needs to iterate. Duplicating new instructions onto

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the tail of a block may make that block a new candidate for duplication.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@89264 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Bob Wilson 2009-11-18 22:52:37 +00:00
parent 79d621035e
commit 60f34b9fb0
2 changed files with 71 additions and 3 deletions
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10
lib/CodeGen/BranchFolding.cpp
View File

@ -197,7 +197,6 @@ bool BranchFolder::OptimizeFunction(MachineFunction &MF,
MadeChange |= OptimizeImpDefsBlock(MBB);
}
bool MadeChangeThisIteration = true;
while (MadeChangeThisIteration) {
MadeChangeThisIteration = false;
@ -206,10 +205,15 @@ bool BranchFolder::OptimizeFunction(MachineFunction &MF,
MadeChange |= MadeChangeThisIteration;
}
// Do tail duplication once after tail merging is done. Otherwise it is
// Do tail duplication after tail merging is done. Otherwise it is
// tough to avoid situations where tail duplication and tail merging undo
// each other's transformations ad infinitum.
MadeChange |= TailDuplicateBlocks(MF);
MadeChangeThisIteration = true;
while (MadeChangeThisIteration) {
MadeChangeThisIteration = false;
MadeChangeThisIteration |= TailDuplicateBlocks(MF);
MadeChange |= MadeChangeThisIteration;
}
// See if any jump tables have become mergable or dead as the code generator
// did its thing.

64
test/CodeGen/ARM/tail-opts.ll Normal file
View File

@ -0,0 +1,64 @@
; RUN: llc < %s -march=arm -mcpu=cortex-a8 -asm-verbose=false | FileCheck %s
declare void @bar(i32)
declare void @car(i32)
declare void @dar(i32)
declare void @ear(i32)
declare void @far(i32)
declare i1 @qux()
@GHJK = global i32 0
declare i8* @choose(i8*, i8*);
; BranchFolding should tail-duplicate the indirect jump to avoid
; redundant branching.
; CHECK: tail_duplicate_me:
; CHECK: qux
; CHECK: qux
; CHECK: ldr r{{.}}, LCPI
; CHECK: str r
; CHECK-NEXT: bx r
; CHECK: ldr r{{.}}, LCPI
; CHECK: str r
; CHECK-NEXT: bx r
; CHECK: ldr r{{.}}, LCPI
; CHECK: str r
; CHECK-NEXT: bx r
define void @tail_duplicate_me() nounwind {
entry:
%a = call i1 @qux()
%c = call i8* @choose(i8* blockaddress(@tail_duplicate_me, %return),
i8* blockaddress(@tail_duplicate_me, %altret))
br i1 %a, label %A, label %next
next:
%b = call i1 @qux()
br i1 %b, label %B, label %C
A:
call void @bar(i32 0)
store i32 0, i32* @GHJK
br label %M
B:
call void @car(i32 1)
store i32 0, i32* @GHJK
br label %M
C:
call void @dar(i32 2)
store i32 0, i32* @GHJK
br label %M
M:
indirectbr i8* %c, [label %return, label %altret]
return:
call void @ear(i32 1000)
ret void
altret:
call void @far(i32 1001)
ret void
}