1 files changed, 58 insertions, 0 deletions
diff --git a/test/Transforms/LoopStrengthReduce/X86/lsr-expand-quadratic.ll b/test/Transforms/LoopStrengthReduce/X86/lsr-expand-quadratic.ll
new file mode 100644
index 0000000000000..a7731bfcec565
--- /dev/null
+++ b/test/Transforms/LoopStrengthReduce/X86/lsr-expand-quadratic.ll
@@ -0,0 +1,58 @@
+; REQUIRES: x86
+; RUN: opt -loop-reduce -S < %s | FileCheck %s
+
+; Strength reduction analysis here relies on IV Users analysis, that
+; only finds users among instructions with types that are treated as
+; legal by the data layout. When running this test on pure non-x86
+; configs (for example, ARM 64), it gets confused with the target
+; triple and uses a default data layout instead. This default layout
+; does not have any legal types (even i32), so the transformation
+; does not happen.
+
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
+target triple = "x86_64-apple-macosx"
+
+; PR15470: LSR miscompile. The test2 function should return '1'.
+;
+; SCEV expander cannot expand quadratic recurrences outside of the
+; loop. This recurrence depends on %sub.us, so can't be expanded.
+; We cannot fold SCEVUnknown (sub.us) with recurrences since it is
+; declared after the loop.
+;
+; CHECK-LABEL: @test2
+; CHECK-LABEL: test2.loop:
+; CHECK:  %lsr.iv1 = phi i32 [ %lsr.iv.next2, %test2.loop ], [ -16777216, %entry ]
+; CHECK:  %lsr.iv = phi i32 [ %lsr.iv.next, %test2.loop ], [ -1, %entry ]
+; CHECK:  %lsr.iv.next = add nsw i32 %lsr.iv, 1
+; CHECK:  %lsr.iv.next2 = add nsw i32 %lsr.iv1, 16777216
+;
+; CHECK-LABEL: for.end:
+; CHECK:  %tobool.us = icmp eq i32 %lsr.iv.next2, 0
+; CHECK:  %sub.us = select i1 %tobool.us, i32 0, i32 0
+; CHECK:  %1 = sub i32 0, %sub.us
+; CHECK:  %2 = add i32 %1, %lsr.iv.next
+; CHECK:  %sext.us = mul i32 %lsr.iv.next2, %2
+; CHECK:  %f = ashr i32 %sext.us, 24
+; CHECK: ret i32 %f
+define i32 @test2() {
+entry:
+  br label %test2.loop
+
+test2.loop:
+  %inc1115.us = phi i32 [ 0, %entry ], [ %inc11.us, %test2.loop ]
+  %inc11.us = add nsw i32 %inc1115.us, 1
+  %cmp.us = icmp slt i32 %inc11.us, 2
+  br i1 %cmp.us, label %test2.loop, label %for.end
+
+for.end:
+  %tobool.us = icmp eq i32 %inc1115.us, 0
+  %sub.us = select i1 %tobool.us, i32 0, i32 0
+  %mul.us = shl i32 %inc1115.us, 24
+  %sub.cond.us = sub nsw i32 %inc1115.us, %sub.us
+  %sext.us = mul i32 %mul.us, %sub.cond.us
+  %f = ashr i32 %sext.us, 24
+  br label %exit
+
+exit:
+  ret i32 %f
+}