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Tail duplication still needs to iterate. Duplicating new instructions onto
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
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@ -197,7 +197,6 @@ bool BranchFolder::OptimizeFunction(MachineFunction &MF,
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MadeChange |= OptimizeImpDefsBlock(MBB);
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}
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bool MadeChangeThisIteration = true;
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while (MadeChangeThisIteration) {
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MadeChangeThisIteration = false;
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@ -206,10 +205,15 @@ bool BranchFolder::OptimizeFunction(MachineFunction &MF,
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MadeChange |= MadeChangeThisIteration;
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}
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// Do tail duplication once after tail merging is done. Otherwise it is
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// Do tail duplication after tail merging is done. Otherwise it is
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// tough to avoid situations where tail duplication and tail merging undo
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// each other's transformations ad infinitum.
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MadeChange |= TailDuplicateBlocks(MF);
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MadeChangeThisIteration = true;
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while (MadeChangeThisIteration) {
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MadeChangeThisIteration = false;
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MadeChangeThisIteration |= TailDuplicateBlocks(MF);
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MadeChange |= MadeChangeThisIteration;
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}
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// See if any jump tables have become mergable or dead as the code generator
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// did its thing.
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64
test/CodeGen/ARM/tail-opts.ll
Normal file
64
test/CodeGen/ARM/tail-opts.ll
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@ -0,0 +1,64 @@
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; RUN: llc < %s -march=arm -mcpu=cortex-a8 -asm-verbose=false | FileCheck %s
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declare void @bar(i32)
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declare void @car(i32)
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declare void @dar(i32)
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declare void @ear(i32)
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declare void @far(i32)
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declare i1 @qux()
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@GHJK = global i32 0
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declare i8* @choose(i8*, i8*);
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; BranchFolding should tail-duplicate the indirect jump to avoid
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; redundant branching.
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; CHECK: tail_duplicate_me:
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; CHECK: qux
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; CHECK: qux
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; CHECK: ldr r{{.}}, LCPI
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; CHECK: str r
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; CHECK-NEXT: bx r
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; CHECK: ldr r{{.}}, LCPI
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; CHECK: str r
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; CHECK-NEXT: bx r
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; CHECK: ldr r{{.}}, LCPI
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; CHECK: str r
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; CHECK-NEXT: bx r
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define void @tail_duplicate_me() nounwind {
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entry:
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%a = call i1 @qux()
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%c = call i8* @choose(i8* blockaddress(@tail_duplicate_me, %return),
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i8* blockaddress(@tail_duplicate_me, %altret))
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br i1 %a, label %A, label %next
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next:
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%b = call i1 @qux()
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br i1 %b, label %B, label %C
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A:
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call void @bar(i32 0)
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store i32 0, i32* @GHJK
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br label %M
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B:
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call void @car(i32 1)
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store i32 0, i32* @GHJK
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br label %M
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C:
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call void @dar(i32 2)
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store i32 0, i32* @GHJK
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br label %M
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M:
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indirectbr i8* %c, [label %return, label %altret]
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return:
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call void @ear(i32 1000)
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ret void
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altret:
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call void @far(i32 1001)
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ret void
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}
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