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612785f908
Fixes PR13371: indvars pass incorrectly substitutes 'undef' values. I do not like this fix. It's needed until/unless the meaning of undef changes. It attempts to be complete according to the IR spec, but I don't have much confidence in the implementation given the difficulty testing undefined behavior. Worse, this invalidates some of my hard-fought work on indvars and LSR to optimize pointer induction variables. It results benchmark regressions, which I'll track internally. On x86_64 no LTO I see: -3% huffbench -3% 400.perlbench -8% fhourstones My only suggestion for recovering is to change the meaning of undef. If we could trust an arbitrary instruction to produce a some real value that can be manipulated (e.g. incremented) according to non-undef rules, then this case could be easily handled with SCEV. llvm-svn: 160421
23 lines
978 B
LLVM
23 lines
978 B
LLVM
; RUN: opt < %s -indvars -S | FileCheck %s
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; PR13371: indvars pass incorrectly substitutes 'undef' values
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;
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; LFTR should not user %undef as the loop counter.
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; CHECK: @test
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; CHECK-NOT: icmp{{.*}}undef
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@.str3 = private constant [6 x i8] c"%lld\0A\00", align 1
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declare i32 @printf(i8* noalias nocapture, ...) nounwind
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define i64 @test() nounwind {
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func_start:
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br label %block9
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block9: ; preds = %block9,%func_start
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%undef = phi i64 [ %next_undef, %block9 ], [ undef, %func_start ]
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%iter = phi i64 [ %next_iter, %block9 ], [ 1, %func_start ]
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%next_iter = add nsw i64 %iter, 1
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%0 = tail call i32 (i8*, ...)* @printf(i8* noalias nocapture getelementptr inbounds ([6 x i8]* @.str3, i64 0, i64 0), i64 %next_iter, i64 %undef)
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%next_undef = add nsw i64 %undef, 1
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%_tmp_3 = icmp slt i64 %next_iter, 100
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br i1 %_tmp_3, label %block9, label %exit
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exit: ; preds = %block9
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ret i64 0
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}
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