[LoopVectorize] Use MapVector rather than DenseMap for MinBWs.

The order in which instructions are truncated in truncateToMinimalBitwidths
effects code generation. Switch to a map with a determinisic order, since the
iteration order over a DenseMap is not defined.

This code is not hot, so the difference in container performance isn't
interesting.

Many thanks to David Blaikie for making me aware of MapVector!

Fixes PR25490.

Differential Revision: http://reviews.llvm.org/D14981

llvm-svn: 254179

1 files changed, 54 insertions, 0 deletions

diff --git a/llvm/test/Transforms/LoopVectorize/AArch64/deterministic-type-shrinkage.ll b/llvm/test/Transforms/LoopVectorize/AArch64/deterministic-type-shrinkage.ll
new file mode 100644
index 00000000000..65f5c4e6266
--- /dev/null
+++ b/llvm/test/Transforms/LoopVectorize/AArch64/deterministic-type-shrinkage.ll
@@ -0,0 +1,54 @@
+; RUN: opt -S < %s -loop-vectorize -instcombine 2>&1 | FileCheck %s
+
+target datalayout = "e-m:e-i64:64-i128:128-n32:64-S128"
+target triple = "aarch64"
+
+;; See https://llvm.org/bugs/show_bug.cgi?id=25490
+;; Due to the data structures used, the LLVM IR was not determinisic.
+;; This test comes from the PR.
+
+;; CHECK-LABEL: @test(
+; CHECK: load <16 x i8>
+; CHECK-NEXT: getelementptr
+; CHECK-NEXT: bitcast
+; CHECK-NEXT: load <16 x i8>
+; CHECK-NEXT: zext <16 x i8>
+; CHECK-NEXT: zext <16 x i8>
+define void @test(i32 %n, i8* nocapture %a, i8* nocapture %b, i8* nocapture readonly %c) {
+entry:
+  %cmp.28 = icmp eq i32 %n, 0
+  br i1 %cmp.28, label %for.cond.cleanup, label %for.body.preheader
+
+for.body.preheader:                               ; preds = %entry
+  br label %for.body
+
+for.cond.cleanup.loopexit:                        ; preds = %for.body
+  br label %for.cond.cleanup
+
+for.cond.cleanup:                                 ; preds = %for.cond.cleanup.loopexit, %entry
+  ret void
+
+for.body:                                         ; preds = %for.body.preheader, %for.body
+  %indvars.iv = phi i64 [ %indvars.iv.next, %for.body ], [ 0, %for.body.preheader ]
+  %arrayidx = getelementptr inbounds i8, i8* %c, i64 %indvars.iv
+  %0 = load i8, i8* %arrayidx, align 1
+  %conv = zext i8 %0 to i32
+  %arrayidx2 = getelementptr inbounds i8, i8* %a, i64 %indvars.iv
+  %1 = load i8, i8* %arrayidx2, align 1
+  %conv3 = zext i8 %1 to i32
+  %mul = mul nuw nsw i32 %conv3, %conv
+  %shr.26 = lshr i32 %mul, 8
+  %conv4 = trunc i32 %shr.26 to i8
+  store i8 %conv4, i8* %arrayidx2, align 1
+  %arrayidx8 = getelementptr inbounds i8, i8* %b, i64 %indvars.iv
+  %2 = load i8, i8* %arrayidx8, align 1
+  %conv9 = zext i8 %2 to i32
+  %mul10 = mul nuw nsw i32 %conv9, %conv
+  %shr11.27 = lshr i32 %mul10, 8
+  %conv12 = trunc i32 %shr11.27 to i8
+  store i8 %conv12, i8* %arrayidx8, align 1
+  %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
+  %lftr.wideiv = trunc i64 %indvars.iv.next to i32
+  %exitcond = icmp eq i32 %lftr.wideiv, %n
+  br i1 %exitcond, label %for.cond.cleanup.loopexit, label %for.body
+}