[llvm] 2c6f78d - [InstCombine] add tests for icmp with sub with multiple uses; NFC

[Sanjay Patel via llvm-commits]

Author: Sanjay Patel
Date: 2022-04-01T13:39:24-04:00
New Revision: 2c6f78dc2c3eab050e8ef21d5ca0064a88053792

URL: https://github.com/llvm/llvm-project/commit/2c6f78dc2c3eab050e8ef21d5ca0064a88053792
DIFF: https://github.com/llvm/llvm-project/commit/2c6f78dc2c3eab050e8ef21d5ca0064a88053792.diff

LOG: [InstCombine] add tests for icmp with sub with multiple uses; NFC

Issue #54558

Added: 
    

Modified: 
    llvm/test/Transforms/InstCombine/icmp-sub.ll

Removed: 
    


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diff  --git a/llvm/test/Transforms/InstCombine/icmp-sub.ll b/llvm/test/Transforms/InstCombine/icmp-sub.ll
index 0541f2f0f1369..026560d5c6da2 100644
--- a/llvm/test/Transforms/InstCombine/icmp-sub.ll
+++ b/llvm/test/Transforms/InstCombine/icmp-sub.ll
@@ -501,3 +501,61 @@ define i32 @sub_eq_zero_select(i32 %a, i32 %b, i32* %p) {
   %sel = select i1 %cmp, i32 %a, i32 %b
   ret i32 %sel
 }
+
+; TODO: Replacing the "SUB == 0" regresses codegen, and it may be hard to recover from that.
+
+declare i32 @llvm.umin.i32(i32, i32)
+
+define void @PR54558_reduced(i32 %arg) {
+; CHECK-LABEL: @PR54558_reduced(
+; CHECK-NEXT:  bb_entry:
+; CHECK-NEXT:    br label [[BB_LOOP:%.*]]
+; CHECK:       bb_loop:
+; CHECK-NEXT:    [[PHI_OUTER:%.*]] = phi i32 [ [[SUB:%.*]], [[BB_LOOP]] ], [ [[ARG:%.*]], [[BB_ENTRY:%.*]] ]
+; CHECK-NEXT:    [[MIN:%.*]] = tail call i32 @llvm.umin.i32(i32 [[PHI_OUTER]], i32 43)
+; CHECK-NEXT:    call void @use(i32 [[MIN]])
+; CHECK-NEXT:    [[SUB]] = sub i32 [[PHI_OUTER]], [[MIN]]
+; CHECK-NEXT:    [[COND_OUTER:%.*]] = icmp ult i32 [[PHI_OUTER]], 44
+; CHECK-NEXT:    br i1 [[COND_OUTER]], label [[BB_EXIT:%.*]], label [[BB_LOOP]]
+; CHECK:       bb_exit:
+; CHECK-NEXT:    ret void
+;
+bb_entry:
+  br label %bb_loop
+
+bb_loop:
+  %phi_outer = phi i32 [ %sub, %bb_loop ], [ %arg, %bb_entry ]
+  %min = tail call i32 @llvm.umin.i32(i32 %phi_outer, i32 43)
+  call void @use(i32 %min)
+  %sub = sub i32 %phi_outer, %min
+  %cond_outer = icmp eq i32 %sub, 0
+  br i1 %cond_outer, label %bb_exit, label %bb_loop
+
+bb_exit:
+  ret void
+}
+
+define void @PR54558_reduced_more(i32 %x, i32 %y) {
+; CHECK-LABEL: @PR54558_reduced_more(
+; CHECK-NEXT:  bb_entry:
+; CHECK-NEXT:    br label [[BB_LOOP:%.*]]
+; CHECK:       bb_loop:
+; CHECK-NEXT:    [[PHI_OUTER:%.*]] = phi i32 [ [[SUB:%.*]], [[BB_LOOP]] ], [ [[X:%.*]], [[BB_ENTRY:%.*]] ]
+; CHECK-NEXT:    [[SUB]] = sub i32 [[PHI_OUTER]], [[Y:%.*]]
+; CHECK-NEXT:    [[COND_OUTER:%.*]] = icmp eq i32 [[PHI_OUTER]], [[Y]]
+; CHECK-NEXT:    br i1 [[COND_OUTER]], label [[BB_EXIT:%.*]], label [[BB_LOOP]]
+; CHECK:       bb_exit:
+; CHECK-NEXT:    ret void
+;
+bb_entry:
+  br label %bb_loop
+
+bb_loop:
+  %phi_outer = phi i32 [ %sub, %bb_loop ], [ %x, %bb_entry ]
+  %sub = sub i32 %phi_outer, %y
+  %cond_outer = icmp eq i32 %sub, 0
+  br i1 %cond_outer, label %bb_exit, label %bb_loop
+
+bb_exit:
+  ret void
+}