[DAGCombine][ARM] x ==/!= c -> (x - c) ==/!= 0 iff '-c' can be folded into the x node.

Summary:
This fold, helps recover from the rest of the D62266 ARM regressions.
https://rise4fun.com/Alive/TvpC

Note that while the fold is quite flexible, i've restricted it
to the single interesting pattern at the moment.

Reviewers: efriedma, craig.topper, spatel, RKSimon, deadalnix

Reviewed By: deadalnix

Subscribers: javed.absar, kristof.beyls, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D62450

1 files changed, 18 insertions, 44 deletions

diff --git a/llvm/test/CodeGen/ARM/addsubcarry-promotion.ll b/llvm/test/CodeGen/ARM/addsubcarry-promotion.ll
index aaf7189a6bb..ea670e5584e 100644
--- a/llvm/test/CodeGen/ARM/addsubcarry-promotion.ll
+++ b/llvm/test/CodeGen/ARM/addsubcarry-promotion.ll
@@ -14,61 +14,35 @@ define void @fn1(i32 %a, i32 %b, i32 %c) local_unnamed_addr #0 {
 ; ARM-NEXT:    adds r0, r1, r0
 ; ARM-NEXT:    movw r1, #65535
 ; ARM-NEXT:    sxth r2, r2
-; ARM-NEXT:    adc r0, r2, #0
-; ARM-NEXT:    uxth r0, r0
-; ARM-NEXT:    cmp r0, r1
+; ARM-NEXT:    adc r0, r2, #1
+; ARM-NEXT:    tst r0, r1
 ; ARM-NEXT:    bxeq lr
 ; ARM-NEXT:  .LBB0_1: @ %for.cond
 ; ARM-NEXT:    @ =>This Inner Loop Header: Depth=1
 ; ARM-NEXT:    b .LBB0_1
 ;
-; THUMBV6M-LABEL: fn1:
-; THUMBV6M:       @ %bb.0: @ %entry
-; THUMBV6M-NEXT:    rsbs r2, r2, #0
-; THUMBV6M-NEXT:    sxth r2, r2
-; THUMBV6M-NEXT:    movs r3, #0
-; THUMBV6M-NEXT:    adds r0, r1, r0
-; THUMBV6M-NEXT:    adcs r3, r2
-; THUMBV6M-NEXT:    uxth r0, r3
-; THUMBV6M-NEXT:    ldr r1, .LCPI0_0
-; THUMBV6M-NEXT:    cmp r0, r1
-; THUMBV6M-NEXT:    beq .LBB0_2
-; THUMBV6M-NEXT:  .LBB0_1: @ %for.cond
-; THUMBV6M-NEXT:    @ =>This Inner Loop Header: Depth=1
-; THUMBV6M-NEXT:    b .LBB0_1
-; THUMBV6M-NEXT:  .LBB0_2: @ %if.end
-; THUMBV6M-NEXT:    bx lr
-; THUMBV6M-NEXT:    .p2align 2
-; THUMBV6M-NEXT:  @ %bb.3:
-; THUMBV6M-NEXT:  .LCPI0_0:
-; THUMBV6M-NEXT:    .long 65535 @ 0xffff
-;
-; THUMBV8M-BASE-LABEL: fn1:
-; THUMBV8M-BASE:       @ %bb.0: @ %entry
-; THUMBV8M-BASE-NEXT:    rsbs r2, r2, #0
-; THUMBV8M-BASE-NEXT:    sxth r2, r2
-; THUMBV8M-BASE-NEXT:    movs r3, #0
-; THUMBV8M-BASE-NEXT:    adds r0, r1, r0
-; THUMBV8M-BASE-NEXT:    adcs r3, r2
-; THUMBV8M-BASE-NEXT:    uxth r0, r3
-; THUMBV8M-BASE-NEXT:    movw r1, #65535
-; THUMBV8M-BASE-NEXT:    cmp r0, r1
-; THUMBV8M-BASE-NEXT:    beq .LBB0_2
-; THUMBV8M-BASE-NEXT:  .LBB0_1: @ %for.cond
-; THUMBV8M-BASE-NEXT:    @ =>This Inner Loop Header: Depth=1
-; THUMBV8M-BASE-NEXT:    b .LBB0_1
-; THUMBV8M-BASE-NEXT:  .LBB0_2: @ %if.end
-; THUMBV8M-BASE-NEXT:    bx lr
+; THUMB1-LABEL: fn1:
+; THUMB1:       @ %bb.0: @ %entry
+; THUMB1-NEXT:    rsbs r2, r2, #0
+; THUMB1-NEXT:    sxth r2, r2
+; THUMB1-NEXT:    movs r3, #1
+; THUMB1-NEXT:    adds r0, r1, r0
+; THUMB1-NEXT:    adcs r3, r2
+; THUMB1-NEXT:    lsls r0, r3, #16
+; THUMB1-NEXT:    beq .LBB0_2
+; THUMB1-NEXT:  .LBB0_1: @ %for.cond
+; THUMB1-NEXT:    @ =>This Inner Loop Header: Depth=1
+; THUMB1-NEXT:    b .LBB0_1
+; THUMB1-NEXT:  .LBB0_2: @ %if.end
+; THUMB1-NEXT:    bx lr
 ;
 ; THUMB-LABEL: fn1:
 ; THUMB:       @ %bb.0: @ %entry
 ; THUMB-NEXT:    rsbs r2, r2, #0
 ; THUMB-NEXT:    adds r0, r0, r1
-; THUMB-NEXT:    movw r1, #65535
 ; THUMB-NEXT:    sxth r2, r2
-; THUMB-NEXT:    adc r0, r2, #0
-; THUMB-NEXT:    uxth r0, r0
-; THUMB-NEXT:    cmp r0, r1
+; THUMB-NEXT:    adc r0, r2, #1
+; THUMB-NEXT:    lsls r0, r0, #16
 ; THUMB-NEXT:    it eq
 ; THUMB-NEXT:    bxeq lr
 ; THUMB-NEXT:  .LBB0_1: @ %for.cond