simple loop pessimized by -std-compile-opts

[nlewycky]

Bugzilla Link	3760
Resolution	INVALID
Resolved on	Nov 07, 2018 00:17
Version	trunk
OS	Linux
CC	@sunfishcode

Extended Description

This simple program:

define void @​test(i32 %x, i32** %y) {
entry:
br label %loop

loop: ; preds = %loop, %entry
%tmp = phi i32 [ 0, %entry ], [ %tmp1, %loop ] ; [#uses=1]
%tmp1 = add i32 %tmp, 1 ; [#uses=2]
%my = malloc i32 ; <i32*> [#uses=1]
%z = getelementptr i32** %y, i32 %tmp
store i32* %my, i32** %z
%done = icmp eq i32 %tmp1, %x ; [#uses=1]
br i1 %done, label %out, label %loop

out: ; preds = %loop
ret void
}

is rewritten to use i64 induction variable and then zext/sext/trunc is added all over to fix it up. On x86 the resulting .s is much worse.

[lattner]

Try adding a x86-32 target triple. Without it, the optimizer defaults to optimizing for sparc 64.

[nlewycky]

Thanks Chris! That does indeed fix everything.