Closed
Description
I tried this IR/MIR:
; ModuleID = 'repro_117902.54923e0577e9cdaf-cgu.0'
source_filename = "repro_117902.54923e0577e9cdaf-cgu.0"
target datalayout = "e-m:o-i64:64-i128:128-n32:64-S128"
target triple = "arm64-apple-macosx11.0.0"
define i1 @foo(i32 %self.0.val, i8 %self.4.val) #1 {
start:
switch i32 %self.0.val, label %bb2 [
i32 0, label %bb9
i32 1, label %bb4
i32 2, label %bb5
i32 3, label %bb1
]
bb2: ; preds = %start
unreachable
bb4: ; preds = %start
br label %bb9
bb5: ; preds = %start
br label %bb9
bb1: ; preds = %start
%trunc.not = icmp eq i8 %self.4.val, 0
br label %bb9
bb9: ; preds = %bb1, %start, %bb5, %bb4
%r = phi i1 [ true, %bb5 ], [ true, %bb4 ], [ false, %start ], [ %trunc.not, %bb1 ]
ret i1 %r
}
attributes #1 = { "frame-pointer"="non-leaf" "target-cpu"="apple-m1" }I got:
_foo: ; @foo
mov x8, x0
mov w0, #0 ; =0x0
adrp x9, LJTI0_0@PAGE
add x9, x9, LJTI0_0@PAGEOFF
adr x10, LBB0_1
ldrb w11, [x9, x8]
add x10, x10, x11, lsl #2
br x10
...
If I run with -O1:
_foo: ; @foo
mov x8, x0
mov w8, w0
mov w0, #0 ; =0x0
adrp x9, LJTI0_0@PAGE
add x9, x9, LJTI0_0@PAGEOFF
adr x10, LBB0_1
ldrb w11, [x9, x8]
add x10, x10, x11, lsl #2
br x10
I think the first instruction should be mov w8, w0.
I'm not familiar with the MIR. But it looks like postrapseudos created mov x8, x0 in lowercopy.
Then machine-cp removes late mov w8, w0.
godbolt: https://llvm.godbolt.org/z/1hfYvrGPG
from: rust-lang/rust#117902