[PATCH] D90162: [llvm][AArch64] Prevent spurious zero extension.

[Francesco Petrogalli via Phabricator via llvm-commits]

fpetrogalli added inline comments.


================
Comment at: llvm/test/CodeGen/ARM/select-imm.ll:221
 ; ARMT2-LABEL: t9:
-; ARMT2: bl f
-; ARMT2: uxtb r0, r4
-; ARMT2: cmp  r0, r0
-; ARMT2: add  r1, r4, #1
-; ARMT2: mov  r2, r0
-; ARMT2: add  r2, r2, #1
-; ARMT2: add  r1, r1, #1
-; ARMT2: uxtb r3, r2
-; ARMT2: cmp  r3, r0
+; ARMT2:       .save   {r4, lr}
+; ARMT2:       push    {r4, lr}
----------------
For reference, this test has changed as follows:

```
;       OLD                     NEW
;       .save   {r4, lr}        .save   {r4, lr}
;       push    {r4, lr}        push    {r4, lr}
;       ldrsb   r4, [r0]        ldrb    r4, [r0]
;       mov     r0, #1          mov     r0, #1
;       bl      f               bl      f
;       uxtb    r0, r4          cmp     r4, r4
;       cmp     r0, r0          popne   {r4, pc}
;       popne   {r4, pc}     .LBB0_1:
; .LBB0_1:                      sxtb    r0, r4
;       add     r1, r4, #1      add     r0, r0, #1
;       mov     r2, r0          mov     r1, r4
; .LBB0_2:                   .LBB0_2:
;       add     r2, r2, #1      add     r1, r1, #1
;       add     r1, r1, #1      add     r0, r0, #1
;       uxtb    r3, r2          uxtb    r2, r1
;       cmp     r3, r0          cmp     r2, r4
;       blt     .LBB0_2         blt     .LBB0_2
;       pop     {r4, pc}        pop     {r4, pc}
```


================
Comment at: llvm/test/CodeGen/ARM/select-imm.ll:240
 
 ; THUMB1-LABEL: t9:
+; THUMB1:          .save   {r4, lr}
----------------
For reference, this output has changed as follows:

```
; OLD                            NEW
;         .save   {r4, lr}               .save   {r4, lr}
;         push    {r4, lr}               push    {r4, lr}
;         movs    r2, #0                 ldrb    r4, [r0]
;         rsbs    r1, r2, #0             movs    r0, #1
;         adcs    r1, r2                 bl      f
;         ldrb    r4, [r0]               cmp     r4, r4
;         mov     r0, r1                 bne     .LBB0_3
;         bl      f                      sxtb    r0, r4
;         sxtb    r1, r4                 adds    r0, r0, #1
;         uxtb    r0, r1                 mov     r1, r4
;         cmp     r0, r0         .LBB0_2:
;         bne     .LBB0_3                adds    r0, r0, #1
;         adds    r1, r1, #1             adds    r1, r1, #1
;         mov     r2, r0                 uxtb    r2, r1
; .LBB0_2:                               cmp     r2, r4
;         adds    r1, r1, #1             blt     .LBB0_2
;         adds    r2, r2, #1     .LBB0_3:
;         uxtb    r3, r2                 pop     {r4, pc}
;         cmp     r3, r0
;         blt     .LBB0_2
; .LBB0_3:
;         pop     {r4, pc}
```


================
Comment at: llvm/test/CodeGen/ARM/select-imm.ll:260
 
 ; THUMB2-LABEL: t9:
+; THUMB2:          .save   {r4, lr}
----------------
For reference, this has changed as follows:

```
; OLD                         NEW
;         .save   {r4, lr}            .save   {r4, lr}
;         push    {r4, lr}            push    {r4, lr}
;         ldrsb.w r4, [r0]            ldrb    r4, [r0]
;         movs    r0, #1              movs    r0, #1
;         bl      f                   bl      f
;         uxtb    r0, r4              cmp     r4, r4
;         cmp     r0, r0              it      ne
;         it      ne                  popne   {r4, pc}
;         popne   {r4, pc}    .LBB0_1:
; .LBB0_1:                            sxtb    r0, r4
;         adds    r1, r4, #1          adds    r0, #1
;         mov     r2, r0              mov     r1, r4
; .LBB0_2:                    .LBB0_2:
;         adds    r2, #1              adds    r1, #1
;         adds    r1, #1              adds    r0, #1
;         uxtb    r3, r2              uxtb    r2, r1
;         cmp     r3, r0              cmp     r2, r4
;         blt     .LBB0_2             blt     .LBB0_2
;         pop     {r4, pc}            pop     {r4, pc}
```


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D90162/new/

https://reviews.llvm.org/D90162