[llvm] b5ae700 - [StackSafety] Simplify SCEVRewriteVisitor

[Vitaly Buka via llvm-commits]

Author: Vitaly Buka
Date: 2020-05-26T18:09:43-07:00
New Revision: b5ae70046b0211ff75be8459f7282fe07ad918d8

URL: https://github.com/llvm/llvm-project/commit/b5ae70046b0211ff75be8459f7282fe07ad918d8
DIFF: https://github.com/llvm/llvm-project/commit/b5ae70046b0211ff75be8459f7282fe07ad918d8.diff

LOG: [StackSafety] Simplify SCEVRewriteVisitor

Probably NFC.

Added: 
    

Modified: 
    llvm/lib/Analysis/StackSafetyAnalysis.cpp
    llvm/test/Analysis/StackSafetyAnalysis/local.ll

Removed: 
    


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diff  --git a/llvm/lib/Analysis/StackSafetyAnalysis.cpp b/llvm/lib/Analysis/StackSafetyAnalysis.cpp
index 4b2fc300b118..10b9f14bc75a 100644
--- a/llvm/lib/Analysis/StackSafetyAnalysis.cpp
+++ b/llvm/lib/Analysis/StackSafetyAnalysis.cpp
@@ -42,16 +42,6 @@ class AllocaOffsetRewriter : public SCEVRewriteVisitor<AllocaOffsetRewriter> {
   AllocaOffsetRewriter(ScalarEvolution &SE, const Value *AllocaPtr)
       : SCEVRewriteVisitor(SE), AllocaPtr(AllocaPtr) {}
 
-  const SCEV *visit(const SCEV *Expr) {
-    // Only re-write the expression if the alloca is used in an addition
-    // expression (it can be used in other types of expressions if it's cast to
-    // an int and passed as an argument.)
-    if (!isa<SCEVAddRecExpr>(Expr) && !isa<SCEVAddExpr>(Expr) &&
-        !isa<SCEVUnknown>(Expr))
-      return Expr;
-    return SCEVRewriteVisitor<AllocaOffsetRewriter>::visit(Expr);
-  }
-
   const SCEV *visitUnknown(const SCEVUnknown *Expr) {
     // FIXME: look through one or several levels of definitions?
     // This can be inttoptr(AllocaPtr) and SCEV would not unwrap
@@ -237,7 +227,8 @@ ConstantRange StackSafetyLocalAnalysis::offsetFrom(Value *Addr, Value *Base) {
   AllocaOffsetRewriter Rewriter(SE, Base);
   const SCEV *Expr = Rewriter.visit(SE.getSCEV(Addr));
   ConstantRange Offset = SE.getUnsignedRange(Expr).zextOrTrunc(PointerSize);
-  assert(!Offset.isEmptySet());
+  if (Offset.isEmptySet())
+    return UnknownRange;
   return Offset;
 }
 

diff  --git a/llvm/test/Analysis/StackSafetyAnalysis/local.ll b/llvm/test/Analysis/StackSafetyAnalysis/local.ll
index 0ba1694e99eb..b7c9eb1d2953 100644
--- a/llvm/test/Analysis/StackSafetyAnalysis/local.ll
+++ b/llvm/test/Analysis/StackSafetyAnalysis/local.ll
@@ -177,6 +177,7 @@ define void @NonConstantOffset(i1 zeroext %z) {
 ; CHECK-NEXT: args uses:
 ; CHECK-NEXT: z[]: full-set{{$}}
 ; CHECK-NEXT: allocas uses:
+; FIXME: SCEV can't look through selects.
 ; CHECK-NEXT: x[4]: [0,4){{$}}
 ; CHECK-NOT: ]:
 entry: