[PATCH] D158960: [ValueTracking] Handle conflicts when computing knownbits of PHI nodes in deadcode; PR65022
Noah Goldstein via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Mon Aug 28 11:20:25 PDT 2023
goldstein.w.n updated this revision to Diff 554001.
goldstein.w.n added a comment.
Re-reduce test
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D158960/new/
https://reviews.llvm.org/D158960
Files:
llvm/lib/Analysis/ValueTracking.cpp
llvm/test/Analysis/ValueTracking/knownbits-phi-deadcode.ll
Index: llvm/test/Analysis/ValueTracking/knownbits-phi-deadcode.ll
===================================================================
--- /dev/null
+++ llvm/test/Analysis/ValueTracking/knownbits-phi-deadcode.ll
@@ -0,0 +1,57 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 2
+; RUN: opt -passes=loop-deletion -S < %s | FileCheck %s
+; This reduced testcase from pr65022. We are only testing that is doesn't crash.
+
+define void @f(i32 %spec.select) {
+; CHECK-LABEL: define void @f
+; CHECK-SAME: (i32 [[SPEC_SELECT:%.*]]) {
+; CHECK-NEXT: entry:
+; CHECK-NEXT: br label [[L_OUTER:%.*]]
+; CHECK: L.outer:
+; CHECK-NEXT: br label [[IF_END:%.*]]
+; CHECK: if.end:
+; CHECK-NEXT: [[DOTB:%.*]] = load i1, ptr null, align 1
+; CHECK-NEXT: [[TMP0:%.*]] = select i1 [[DOTB]], i32 0, i32 1
+; CHECK-NEXT: [[CMP:%.*]] = icmp sgt i32 [[TMP0]], -1
+; CHECK-NEXT: br i1 [[CMP]], label [[IF_THEN3:%.*]], label [[WHILE_COND_SPLIT_LOOP_EXIT1:%.*]]
+; CHECK: if.then3:
+; CHECK-NEXT: br label [[IF_END]]
+; CHECK: while.cond.split.loop.exit1:
+; CHECK-NEXT: [[DOTLCSSA:%.*]] = phi i32 [ [[TMP0]], [[IF_END]] ]
+; CHECK-NEXT: [[NOT_LE:%.*]] = xor i32 [[DOTLCSSA]], 1
+; CHECK-NEXT: [[TOBOOL7_NOT:%.*]] = icmp eq i32 [[NOT_LE]], 0
+; CHECK-NEXT: [[SPEC_SELECT3:%.*]] = select i1 [[TOBOOL7_NOT]], i32 0, i32 [[SPEC_SELECT]]
+; CHECK-NEXT: [[TOBOOL10_NOT:%.*]] = icmp eq i32 [[SPEC_SELECT3]], 0
+; CHECK-NEXT: br i1 [[TOBOOL10_NOT]], label [[FOR_COND_PREHEADER:%.*]], label [[L_OUTER]]
+; CHECK: for.cond.preheader:
+; CHECK-NEXT: ret void
+;
+entry:
+ br label %L.outer
+
+L.outer: ; preds = %while.cond.split.loop.exit1, %entry
+ br label %if.end
+
+if.end: ; preds = %if.then3, %L.outer
+ %.b = load i1, ptr null, align 1
+ %0 = select i1 %.b, i32 0, i32 1
+ %cmp = icmp sgt i32 %0, -1
+ br i1 %cmp, label %if.then3, label %while.cond.split.loop.exit1
+
+if.then3: ; preds = %if.end
+ br label %if.end
+
+while.cond.split.loop.exit1: ; preds = %if.end
+ %.lcssa = phi i32 [ %0, %if.end ]
+ %not.le = xor i32 %.lcssa, 1
+ %tobool7.not = icmp eq i32 %not.le, 0
+ %spec.select3 = select i1 %tobool7.not, i32 0, i32 %spec.select
+ %tobool10.not = icmp eq i32 %spec.select3, 0
+ br i1 %tobool10.not, label %for.cond.preheader, label %L.outer
+
+for.cond.preheader: ; preds = %while.cond.split.loop.exit1
+ ret void
+}
+
+; uselistorder directives
+uselistorder i32 0, { 1, 0, 2, 3 }
Index: llvm/lib/Analysis/ValueTracking.cpp
===================================================================
--- llvm/lib/Analysis/ValueTracking.cpp
+++ llvm/lib/Analysis/ValueTracking.cpp
@@ -1480,7 +1480,17 @@
Pred = CmpInst::getInversePredicate(Pred);
// Get the knownbits implied by the incoming phi condition.
auto CR = ConstantRange::makeExactICmpRegion(Pred, *RHSC);
- Known2 = Known2.unionWith(CR.toKnownBits());
+ KnownBits KnownUnion = Known2.unionWith(CR.toKnownBits());
+ // We can have conflicts here if we are analyzing deadcode (its
+ // impossible for us reach this BB based the icmp).
+ if (KnownUnion.hasConflict()) {
+ // No reason to continue analyzing in a known dead region, so
+ // just resetAll and break. This will cause us to also exit the
+ // outer loop.
+ Known.resetAll();
+ break;
+ }
+ Known2 = KnownUnion;
}
}
}
-------------- next part --------------
A non-text attachment was scrubbed...
Name: D158960.554001.patch
Type: text/x-patch
Size: 3767 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20230828/a0b65423/attachment.bin>
More information about the llvm-commits
mailing list