[llvm] [SLP]Represent externally used values as original scalars, if profitable. (PR #100904)

[Simon Pilgrim via llvm-commits]

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@@ -44,6 +24,26 @@ define void @foo() {
 ; CHECK-NEXT:    [[PHI7:%.*]] = phi i32 [ [[TMP8]], [[BB4]] ]
 ; CHECK-NEXT:    ret void
 ;
+; FORCED-LABEL: define void @foo() {
+; FORCED-NEXT:  bb:
+; FORCED-NEXT:    [[TMP0:%.*]] = insertelement <2 x i32> <i32 poison, i32 0>, i32 0, i32 0
+; FORCED-NEXT:    br label [[BB1:%.*]]
+; FORCED:       bb1:
+; FORCED-NEXT:    [[TMP1:%.*]] = phi <2 x i32> [ zeroinitializer, [[BB:%.*]] ], [ [[TMP6:%.*]], [[BB4:%.*]] ]
+; FORCED-NEXT:    [[TMP2:%.*]] = shl <2 x i32> [[TMP1]], [[TMP0]]
+; FORCED-NEXT:    [[TMP3:%.*]] = or <2 x i32> [[TMP1]], [[TMP0]]
+; FORCED-NEXT:    [[TMP4:%.*]] = shufflevector <2 x i32> [[TMP2]], <2 x i32> [[TMP3]], <2 x i32> <i32 0, i32 3>
+; FORCED-NEXT:    [[TMP5:%.*]] = shufflevector <2 x i32> [[TMP4]], <2 x i32> [[TMP1]], <2 x i32> <i32 0, i32 3>
+; FORCED-NEXT:    [[TMP6]] = or <2 x i32> [[TMP5]], zeroinitializer
+; FORCED-NEXT:    [[TMP7:%.*]] = extractelement <2 x i32> [[TMP6]], i32 0
+; FORCED-NEXT:    [[CALL:%.*]] = call i64 null(i32 [[TMP7]])
+; FORCED-NEXT:    br label [[BB4]]
+; FORCED:       bb4:
+; FORCED-NEXT:    br i1 false, label [[BB5:%.*]], label [[BB1]]
+; FORCED:       bb5:
+; FORCED-NEXT:    [[TMP8:%.*]] = phi <2 x i32> [ [[TMP4]], [[BB4]] ]
+; FORCED-NEXT:    ret void
+;
 bb:
   br label %bb1
 
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RKSimon wrote:

revert this change? it looks NFC

https://github.com/llvm/llvm-project/pull/100904