https://github.com/llvmbot created https://github.com/llvm/llvm-project/pull/219832
Backport 88f3a791ddb3886cb6fa8d8df1c19e821b7a49b2 Requested by: @dtcxzyw >From 19ca933aeda350e3f0b5bb90d9672e3ec29ba453 Mon Sep 17 00:00:00 2001 From: AZero13 <[email protected]> Date: Sun, 30 Aug 2026 14:21:48 -0400 Subject: [PATCH] [SCCP] Fix missing worklist push for recursive calls that update lattice values (#219826) For a recursive call, the call instruction itself is a user of the function's arguments. Because I == CurI, I->comesBefore(CurI) is false, and the condition triggers an early return. The recursive call instruction was skipped and never pushed back onto the worklist, halting the solver prematurely before reaching a fixpoint. This caused the solver to incorrectly believe arguments were hardcoded constants rather than a wider constant range, resulting in invalid branch folding. The Fix: This patch updates the condition to explicitly check if I comes strictly after CurI. Fixes: https://github.com/llvm/llvm-project/issues/219503 (cherry picked from commit 88f3a791ddb3886cb6fa8d8df1c19e821b7a49b2) --- llvm/lib/Transforms/Utils/SCCPSolver.cpp | 2 +- .../SCCP/ipsccp-recursive-arg-update.ll | 37 +++++++++++++++++++ 2 files changed, 38 insertions(+), 1 deletion(-) create mode 100644 llvm/test/Transforms/SCCP/ipsccp-recursive-arg-update.ll diff --git a/llvm/lib/Transforms/Utils/SCCPSolver.cpp b/llvm/lib/Transforms/Utils/SCCPSolver.cpp index f7e28132ec65c..054d1765f7ebc 100644 --- a/llvm/lib/Transforms/Utils/SCCPSolver.cpp +++ b/llvm/lib/Transforms/Utils/SCCPSolver.cpp @@ -1070,7 +1070,7 @@ void SCCPInstVisitor::pushToWorkList(Instruction *I) { // same blocks that are after the current one, as they will be visited // anyway. We do have to push updates to earlier instructions (e.g. phi // nodes or loads of tracked globals). - if (CurI && I->getParent() == CurI->getParent() && !I->comesBefore(CurI)) + if (CurI && I->getParent() == CurI->getParent() && CurI->comesBefore(I)) return; // Only push instructions in already visited blocks. Otherwise we'll handle // it when we visit the block for the first time. diff --git a/llvm/test/Transforms/SCCP/ipsccp-recursive-arg-update.ll b/llvm/test/Transforms/SCCP/ipsccp-recursive-arg-update.ll new file mode 100644 index 0000000000000..750677077ea1e --- /dev/null +++ b/llvm/test/Transforms/SCCP/ipsccp-recursive-arg-update.ll @@ -0,0 +1,37 @@ +; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 4 +; RUN: opt -S -passes=ipsccp < %s | FileCheck %s + +define void @caller() { +; CHECK-LABEL: define void @caller() { +; CHECK-NEXT: entry: +; CHECK-NEXT: [[CALL:%.*]] = call i32 @f2(i8 0, i8 0) +; CHECK-NEXT: ret void +; +entry: + %call = call i32 @f2(i8 0, i8 0) + ret void +} + +define internal i32 @f2(i8 %a0, i8 %a1) { +; CHECK-LABEL: define internal i32 @f2( +; CHECK-SAME: i8 range(i8 -9, 1) [[A0:%.*]], i8 range(i8 -9, 1) [[A1:%.*]]) { +; CHECK-NEXT: entry: +; CHECK-NEXT: [[CMP_NOT_NOT:%.*]] = icmp eq i8 [[A0]], -9 +; CHECK-NEXT: br i1 [[CMP_NOT_NOT]], label [[COMMON_RET1:%.*]], label [[IF_THEN3:%.*]] +; CHECK: common.ret1: +; CHECK-NEXT: ret i32 poison +; CHECK: if.then3: +; CHECK-NEXT: [[CALL:%.*]] = call i32 @f2(i8 [[A1]], i8 -9) +; CHECK-NEXT: ret i32 poison +; +entry: + %cmp.not.not = icmp eq i8 %a0, -9 + br i1 %cmp.not.not, label %common.ret1, label %if.then3 + +common.ret1: ; preds = %entry + ret i32 0 + +if.then3: ; preds = %entry + %call = call i32 @f2(i8 %a1, i8 -9) + ret i32 %call +} _______________________________________________ llvm-branch-commits mailing list [email protected] https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-branch-commits
