[llvm] IndVarSimplify: improve a test, stripping undef (PR #126069)

[Nikita Popov via llvm-commits]

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@@ -6,46 +6,40 @@
 ; status. This was caught by the expensive check introduced in D86589.
 
 target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
-target triple = "x86_64-unknown-linux-gnu"
 
- at ptr = external global i64
-
-define dso_local void @hoge() local_unnamed_addr {
+define void @hoge(i64 %x, ptr %ptr) {
 ; CHECK-LABEL: @hoge(
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    [[N:%.*]] = sdiv exact i64 undef, 40
-; CHECK-NEXT:    [[TMP0:%.*]] = sub i64 undef, [[N]]
+; CHECK-NEXT:    [[N:%.*]] = sdiv exact i64 [[X:%.*]], 40
 ; CHECK-NEXT:    br label [[HEADER:%.*]]
 ; CHECK:       header:
-; CHECK-NEXT:    [[INDVARS_IV:%.*]] = phi i64 [ [[INDVARS_IV_NEXT:%.*]], [[LATCH:%.*]] ], [ [[TMP0]], [[ENTRY:%.*]] ]
-; CHECK-NEXT:    [[IDX:%.*]] = phi i64 [ [[IDX_NEXT:%.*]], [[LATCH]] ], [ undef, [[ENTRY]] ]
+; CHECK-NEXT:    [[INDVARS_IV:%.*]] = phi i64 [ [[INDVARS_IV_NEXT2:%.*]], [[LATCH:%.*]] ], [ 1, [[ENTRY:%.*]] ]
+; CHECK-NEXT:    [[IDX:%.*]] = phi i64 [ [[IDX_NEXT:%.*]], [[LATCH]] ], [ 0, [[ENTRY]] ]
 ; CHECK-NEXT:    [[COND:%.*]] = icmp sgt i64 [[N]], [[IDX]]
 ; CHECK-NEXT:    br i1 [[COND]], label [[END:%.*]], label [[INNER_PREHEADER:%.*]]
 ; CHECK:       inner.preheader:
 ; CHECK-NEXT:    br label [[INNER:%.*]]
 ; CHECK:       inner:
-; CHECK-NEXT:    [[I:%.*]] = phi i64 [ [[I_NEXT:%.*]], [[INNER]] ], [ 0, [[INNER_PREHEADER]] ]
-; CHECK-NEXT:    [[I_NEXT]] = add nuw i64 [[I]], 1
-; CHECK-NEXT:    store i64 undef, ptr @ptr, align 8
+; CHECK-NEXT:    [[J:%.*]] = phi i64 [ [[I_NEXT:%.*]], [[INNER]] ], [ [[N]], [[INNER_PREHEADER]] ]
+; CHECK-NEXT:    [[I_NEXT]] = add nsw i64 [[J]], 1
+; CHECK-NEXT:    store i64 0, ptr [[PTR:%.*]], align 8
 ; CHECK-NEXT:    [[EXITCOND:%.*]] = icmp ne i64 [[I_NEXT]], [[INDVARS_IV]]
 ; CHECK-NEXT:    br i1 [[EXITCOND]], label [[INNER]], label [[INNER_EXIT:%.*]]
 ; CHECK:       inner_exit:
-; CHECK-NEXT:    [[INDVAR:%.*]] = phi i64 [ [[I_NEXT]], [[INNER]] ]
-; CHECK-NEXT:    [[INDVAR_USE:%.*]] = add i64 [[INDVAR]], 1
 ; CHECK-NEXT:    br label [[LATCH]]
 ; CHECK:       latch:
 ; CHECK-NEXT:    [[IDX_NEXT]] = add nsw i64 [[IDX]], -1
-; CHECK-NEXT:    [[INDVARS_IV_NEXT]] = add i64 [[INDVARS_IV]], -1
+; CHECK-NEXT:    [[INDVARS_IV_NEXT2]] = add nsw i64 [[INDVARS_IV]], -1
 ; CHECK-NEXT:    br label [[HEADER]]
 ; CHECK:       end:
 ; CHECK-NEXT:    ret void
 ;
 entry:                                            ; preds = %entry
-  %n = sdiv exact i64 undef, 40
+  %n = sdiv exact i64 %x, 40
   br label %header
 
 header:                                           ; preds = %latch, %entry
-  %idx = phi i64 [ %idx.next, %latch ], [ undef, %entry ]
+  %idx = phi i64 [ %idx.next, %latch ], [ 0, %entry ]
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nikic wrote:

What happens if you make this one an argument as well? Will that reduce the diff?

https://github.com/llvm/llvm-project/pull/126069