mirror of
https://github.com/c64scene-ar/llvm-6502.git
synced 2024-08-03 15:29:28 +00:00
4781d8ee1c
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. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@160421 91177308-0d34-0410-b5e6-96231b3b80d8
23 lines
978 B
LLVM
23 lines
978 B
LLVM
; RUN: opt < %s -indvars -S | FileCheck %s
|
|
; PR13371: indvars pass incorrectly substitutes 'undef' values
|
|
;
|
|
; LFTR should not user %undef as the loop counter.
|
|
; CHECK: @test
|
|
; CHECK-NOT: icmp{{.*}}undef
|
|
@.str3 = private constant [6 x i8] c"%lld\0A\00", align 1
|
|
declare i32 @printf(i8* noalias nocapture, ...) nounwind
|
|
define i64 @test() nounwind {
|
|
func_start:
|
|
br label %block9
|
|
block9: ; preds = %block9,%func_start
|
|
%undef = phi i64 [ %next_undef, %block9 ], [ undef, %func_start ]
|
|
%iter = phi i64 [ %next_iter, %block9 ], [ 1, %func_start ]
|
|
%next_iter = add nsw i64 %iter, 1
|
|
%0 = tail call i32 (i8*, ...)* @printf(i8* noalias nocapture getelementptr inbounds ([6 x i8]* @.str3, i64 0, i64 0), i64 %next_iter, i64 %undef)
|
|
%next_undef = add nsw i64 %undef, 1
|
|
%_tmp_3 = icmp slt i64 %next_iter, 100
|
|
br i1 %_tmp_3, label %block9, label %exit
|
|
exit: ; preds = %block9
|
|
ret i64 0
|
|
}
|