Index: lib/Transforms/Scalar/LoopIdiomRecognize.cpp =================================================================== --- lib/Transforms/Scalar/LoopIdiomRecognize.cpp +++ lib/Transforms/Scalar/LoopIdiomRecognize.cpp @@ -1035,6 +1035,17 @@ return nullptr; } +// Check if the recurrence variable `VarX` is in the right form to form +// the idiom. Returns the value coerced to a PHINode if so. +static PHINode *getRecurrenceVar(Value *VarX, Instruction *DefX, + BasicBlock *LoopEntry) { + auto *PhiX = dyn_cast(VarX); + if (PhiX && PhiX->getParent() == LoopEntry && + (PhiX->getOperand(0) == DefX || PhiX->getOperand(1) == DefX)) + return PhiX; + return nullptr; +} + /// Return true iff the idiom is detected in the loop. /// /// Additionally: @@ -1110,13 +1121,9 @@ } // step 3: Check the recurrence of variable X - { - PhiX = dyn_cast(VarX1); - if (!PhiX || - (PhiX->getOperand(0) != DefX2 && PhiX->getOperand(1) != DefX2)) { - return false; - } - } + PhiX = getRecurrenceVar(VarX1, DefX2, LoopEntry); + if (!PhiX) + return false; // step 4: Find the instruction which count the population: cnt2 = cnt1 + 1 { @@ -1227,8 +1234,8 @@ VarX = DefX->getOperand(0); // step 3: Check the recurrence of variable X - PhiX = dyn_cast(VarX); - if (!PhiX || (PhiX->getOperand(0) != DefX && PhiX->getOperand(1) != DefX)) + PhiX = getRecurrenceVar(VarX, DefX, LoopEntry); + if (!PhiX) return false; // step 4: Find the instruction which count the CTLZ: cnt.next = cnt + 1 Index: test/Transforms/LoopIdiom/pr33114.ll =================================================================== --- /dev/null +++ test/Transforms/LoopIdiom/pr33114.ll @@ -0,0 +1,35 @@ +; NOTE: Assertions have been autogenerated by utils/update_test_checks.py +; Check that we're not crashing while looking at the recurrence variable. +; RUN: opt -S -loop-idiom %s | FileCheck %s + +define void @tinkywinky() { +; CHECK-LABEL: @tinkywinky( +; CHECK-NEXT: entry: +; CHECK-NEXT: br i1 true, label [[EXIT:%.*]], label [[PH:%.*]] +; CHECK: ph: +; CHECK-NEXT: [[MYPHI:%.*]] = phi i32 [ 1, [[ENTRY:%.*]] ] +; CHECK-NEXT: br label [[IF_END:%.*]] +; CHECK: if.end: +; CHECK-NEXT: [[PATATINO:%.*]] = ashr i32 [[MYPHI]], undef +; CHECK-NEXT: [[TOBOOL:%.*]] = icmp eq i32 [[PATATINO]], 0 +; CHECK-NEXT: br i1 [[TOBOOL]], label [[EXIT_LOOPEXIT:%.*]], label [[IF_END]] +; CHECK: exit.loopexit: +; CHECK-NEXT: br label [[EXIT]] +; CHECK: exit: +; CHECK-NEXT: ret void +; +entry: + br i1 true, label %exit, label %ph + +ph: + %myphi = phi i32 [ 1, %entry ] + br label %if.end + +if.end: + %patatino = ashr i32 %myphi, undef + %tobool = icmp eq i32 %patatino, 0 + br i1 %tobool, label %exit, label %if.end + +exit: + ret void +}