[PATCH] D112573: [IndVarSimplify] Reduce nondeterministic behaviour in visitIVCast.

[Sander de Smalen via Phabricator via llvm-commits]

sdesmalen updated this revision to Diff 385968.
sdesmalen added a comment.

Removed control flow in favor of `WI.IsSigned |= IsSigned;`


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D112573/new/

https://reviews.llvm.org/D112573

Files:
  llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
  llvm/test/Transforms/IndVarSimplify/deterministic-sign.ll


Index: llvm/test/Transforms/IndVarSimplify/deterministic-sign.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/IndVarSimplify/deterministic-sign.ll
@@ -0,0 +1,65 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt "-passes=loop-rotate,indvars" -S < %s | FileCheck %s
+; RUN: opt "-passes=loop-rotate" < %s | opt "-passes=indvars" -S - | FileCheck %s
+
+target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
+target triple = "aarch64-unknown-linux-gnu"
+
+define dso_local float @foo(float* noalias %dst, float* %src, i32 %offset, i32 %N) {
+; CHECK-LABEL: @foo(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[CMP1:%.*]] = icmp slt i32 1, [[N:%.*]]
+; CHECK-NEXT:    br i1 [[CMP1]], label [[FOR_BODY_LR_PH:%.*]], label [[FOR_COND_CLEANUP:%.*]]
+; CHECK:       for.body.lr.ph:
+; CHECK-NEXT:    [[TMP0:%.*]] = sext i32 [[OFFSET:%.*]] to i64
+; CHECK-NEXT:    [[WIDE_TRIP_COUNT:%.*]] = zext i32 [[N]] to i64
+; CHECK-NEXT:    br label [[FOR_BODY:%.*]]
+; CHECK:       for.cond.for.cond.cleanup_crit_edge:
+; CHECK-NEXT:    br label [[FOR_COND_CLEANUP]]
+; CHECK:       for.cond.cleanup:
+; CHECK-NEXT:    ret float undef
+; CHECK:       for.body:
+; CHECK-NEXT:    [[INDVARS_IV:%.*]] = phi i64 [ 1, [[FOR_BODY_LR_PH]] ], [ [[INDVARS_IV_NEXT:%.*]], [[FOR_BODY]] ]
+; CHECK-NEXT:    [[TMP1:%.*]] = add nsw i64 [[INDVARS_IV]], [[TMP0]]
+; CHECK-NEXT:    [[ARRAYIDX:%.*]] = getelementptr inbounds float, float* [[SRC:%.*]], i64 [[TMP1]]
+; CHECK-NEXT:    [[TMP2:%.*]] = load float, float* [[ARRAYIDX]], align 4
+; CHECK-NEXT:    [[TMP3:%.*]] = add nsw i64 [[TMP1]], 1
+; CHECK-NEXT:    [[ARRAYIDX3:%.*]] = getelementptr inbounds float, float* [[SRC]], i64 [[TMP3]]
+; CHECK-NEXT:    [[TMP4:%.*]] = load float, float* [[ARRAYIDX3]], align 4
+; CHECK-NEXT:    [[ADD4:%.*]] = fadd fast float [[TMP2]], [[TMP4]]
+; CHECK-NEXT:    [[ARRAYIDX6:%.*]] = getelementptr inbounds float, float* [[DST:%.*]], i64 [[INDVARS_IV]]
+; CHECK-NEXT:    store float [[ADD4]], float* [[ARRAYIDX6]], align 4
+; CHECK-NEXT:    [[INDVARS_IV_NEXT]] = add nuw nsw i64 [[INDVARS_IV]], 1
+; CHECK-NEXT:    [[EXITCOND:%.*]] = icmp ne i64 [[INDVARS_IV_NEXT]], [[WIDE_TRIP_COUNT]]
+; CHECK-NEXT:    br i1 [[EXITCOND]], label [[FOR_BODY]], label [[FOR_COND_FOR_COND_CLEANUP_CRIT_EDGE:%.*]], !llvm.loop [[LOOP0:![0-9]+]]
+;
+entry:
+  br label %for.cond
+
+for.cond:                                         ; preds = %for.body, %entry
+  %i.0 = phi i32 [ 1, %entry ], [ %inc, %for.body ]
+  %cmp = icmp slt i32 %i.0, %N
+  br i1 %cmp, label %for.body, label %for.cond.cleanup
+
+for.cond.cleanup:                                 ; preds = %for.cond
+  ret float undef
+
+for.body:                                         ; preds = %for.cond
+  %add = add nsw i32 %i.0, %offset
+  %idxprom = sext i32 %add to i64
+  %arrayidx = getelementptr inbounds float, float* %src, i64 %idxprom
+  %0 = load float, float* %arrayidx, align 4
+  %add1 = add nsw i32 %add, 1
+  %idxprom2 = sext i32 %add1 to i64
+  %arrayidx3 = getelementptr inbounds float, float* %src, i64 %idxprom2
+  %1 = load float, float* %arrayidx3, align 4
+  %add4 = fadd fast float %0, %1
+  %idxprom5 = zext i32 %i.0 to i64
+  %arrayidx6 = getelementptr inbounds float, float* %dst, i64 %idxprom5
+  store float %add4, float* %arrayidx6, align 4
+  %inc = add nuw nsw i32 %i.0, 1
+  br label %for.cond, !llvm.loop !1
+}
+
+!1 = distinct !{!1, !2}
+!2 = !{!"llvm.loop.mustprogress"}
Index: llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
+++ llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
@@ -547,18 +547,18 @@
     return;
   }
 
-  if (!WI.WidestNativeType) {
+  if (!WI.WidestNativeType ||
+      Width > SE->getTypeSizeInBits(WI.WidestNativeType)) {
     WI.WidestNativeType = SE->getEffectiveSCEVType(Ty);
     WI.IsSigned = IsSigned;
     return;
   }
 
-  // We extend the IV to satisfy the sign of its first user, arbitrarily.
-  if (WI.IsSigned != IsSigned)
-    return;
-
-  if (Width > SE->getTypeSizeInBits(WI.WidestNativeType))
-    WI.WidestNativeType = SE->getEffectiveSCEVType(Ty);
+  // We extend the IV to satisfy the sign of its user(s), or 'signed'
+  // if there are multiple users with both sign- and zero extensions,
+  // in order not to introduce nondeterministic behaviour based on the
+  // unspecified order of a PHI nodes' users-iterator.
+  WI.IsSigned |= IsSigned;
 }
 
 //===----------------------------------------------------------------------===//


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