[llvm] 4e500df - [IROutliner] Fix phi nodes when self referential within block but doesn't contain branch
Andrew Litteken via llvm-commits
llvm-commits at lists.llvm.org
Mon Mar 21 09:06:50 PDT 2022
Author: Andrew Litteken
Date: 2022-03-21T11:05:15-05:00
New Revision: 4e500df89ec6104771699dbf674afa982d5c672e
URL: https://github.com/llvm/llvm-project/commit/4e500df89ec6104771699dbf674afa982d5c672e
DIFF: https://github.com/llvm/llvm-project/commit/4e500df89ec6104771699dbf674afa982d5c672e.diff
LOG: [IROutliner] Fix phi nodes when self referential within block but doesn't contain branch
When outlining a phi node, if the the incoming branch is a block contained in the region and the branch from that block is not outlined, we create broken code. The fix is to recognize when that branch from the included incoming block is not contained, and ignore the region.
Reviewer: paquette
Differential Revision: https://reviews.llvm.org/D121311
Added:
llvm/test/Transforms/IROutliner/phi-nodes-parent-block-referential.ll
Modified:
llvm/lib/Transforms/IPO/IROutliner.cpp
Removed:
################################################################################
diff --git a/llvm/lib/Transforms/IPO/IROutliner.cpp b/llvm/lib/Transforms/IPO/IROutliner.cpp
index 258a7c7843361..79d767c387e63 100644
--- a/llvm/lib/Transforms/IPO/IROutliner.cpp
+++ b/llvm/lib/Transforms/IPO/IROutliner.cpp
@@ -278,13 +278,29 @@ void OutlinableRegion::splitCandidate() {
// We iterate over the instructions in the region, if we find a PHINode, we
// check if there are predecessors outside of the region, if there are,
// we ignore this region since we are unable to handle the severing of the
- // phi node right now.
+ // phi node right now.
+
+ // TODO: Handle extraneous inputs for PHINodes through variable number of
+ // inputs, similar to how outputs are handled.
BasicBlock::iterator It = StartInst->getIterator();
+ EndBB = BackInst->getParent();
+ BasicBlock *IBlock;
+ bool EndBBTermAndBackInstDifferent = EndBB->getTerminator() != BackInst;
while (PHINode *PN = dyn_cast<PHINode>(&*It)) {
unsigned NumPredsOutsideRegion = 0;
- for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
- if (!BBSet.contains(PN->getIncomingBlock(i)))
+ for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
+ if (!BBSet.contains(PN->getIncomingBlock(i))) {
+ ++NumPredsOutsideRegion;
+ continue;
+ }
+
+ // We must consider the case there the incoming block to the PHINode is
+ // the same as the final block of the OutlinableRegion. If this is the
+ // case, the branch from this block must also be outlined to be valid.
+ IBlock = PN->getIncomingBlock(i);
+ if (IBlock == EndBB && EndBBTermAndBackInstDifferent)
++NumPredsOutsideRegion;
+ }
if (NumPredsOutsideRegion > 1)
return;
@@ -299,11 +315,9 @@ void OutlinableRegion::splitCandidate() {
// If the region ends with a PHINode, but does not contain all of the phi node
// instructions of the region, we ignore it for now.
- if (isa<PHINode>(BackInst)) {
- EndBB = BackInst->getParent();
- if (BackInst != &*std::prev(EndBB->getFirstInsertionPt()))
- return;
- }
+ if (isa<PHINode>(BackInst) &&
+ BackInst != &*std::prev(EndBB->getFirstInsertionPt()))
+ return;
// The basic block gets split like so:
// block: block:
diff --git a/llvm/test/Transforms/IROutliner/phi-nodes-parent-block-referential.ll b/llvm/test/Transforms/IROutliner/phi-nodes-parent-block-referential.ll
new file mode 100644
index 0000000000000..fc96f0ebcc48f
--- /dev/null
+++ b/llvm/test/Transforms/IROutliner/phi-nodes-parent-block-referential.ll
@@ -0,0 +1,100 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --include-generated-funcs
+; RUN: opt -S -verify -iroutliner -ir-outlining-no-cost < %s | FileCheck %s
+
+; Show that we do not outline when all of the phi nodes in the beginning
+; block are included not in the region.
+
+define void @function1(i32* %a, i32* %b) {
+entry:
+ %0 = alloca i32, align 4
+ %c = load i32, i32* %0, align 4
+ %y = add i32 %c, %c
+ br label %test1
+dummy:
+ ret void
+test1:
+ %1 = phi i32 [ %e, %test1 ], [ %y, %entry ]
+ %2 = phi i32 [ %e, %test1 ], [ %y, %entry ]
+ %e = load i32, i32* %0, align 4
+ %3 = add i32 %c, %c
+ %4 = sub i32 %c, %c
+ br i1 true, label %first, label %test1
+first:
+ ret void
+}
+
+define void @function2(i32* %a, i32* %b) {
+entry:
+ %0 = alloca i32, align 4
+ %c = load i32, i32* %0, align 4
+ %y = mul i32 %c, %c
+ br label %test1
+dummy:
+ ret void
+test1:
+ %1 = phi i32 [ %e, %test1 ], [ %y, %entry ]
+ %2 = phi i32 [ %y, %entry ], [ %e, %test1 ]
+ %e = load i32, i32* %0, align 4
+ %3 = add i32 %c, %c
+ %4 = mul i32 %c, %c
+ br i1 true, label %first, label %test1
+first:
+ ret void
+}
+; CHECK-LABEL: @function1(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[E_LOC:%.*]] = alloca i32, align 4
+; CHECK-NEXT: [[TMP0:%.*]] = alloca i32, align 4
+; CHECK-NEXT: [[C:%.*]] = load i32, i32* [[TMP0]], align 4
+; CHECK-NEXT: [[Y:%.*]] = add i32 [[C]], [[C]]
+; CHECK-NEXT: br label [[TEST1:%.*]]
+; CHECK: dummy:
+; CHECK-NEXT: ret void
+; CHECK: test1:
+; CHECK-NEXT: [[TMP1:%.*]] = phi i32 [ [[E_RELOAD:%.*]], [[TEST1]] ], [ [[Y]], [[ENTRY:%.*]] ]
+; CHECK-NEXT: [[TMP2:%.*]] = phi i32 [ [[E_RELOAD]], [[TEST1]] ], [ [[Y]], [[ENTRY]] ]
+; CHECK-NEXT: [[LT_CAST:%.*]] = bitcast i32* [[E_LOC]] to i8*
+; CHECK-NEXT: call void @llvm.lifetime.start.p0i8(i64 -1, i8* [[LT_CAST]])
+; CHECK-NEXT: call void @outlined_ir_func_0(i32* [[TMP0]], i32 [[C]], i32* [[E_LOC]])
+; CHECK-NEXT: [[E_RELOAD]] = load i32, i32* [[E_LOC]], align 4
+; CHECK-NEXT: call void @llvm.lifetime.end.p0i8(i64 -1, i8* [[LT_CAST]])
+; CHECK-NEXT: [[TMP3:%.*]] = sub i32 [[C]], [[C]]
+; CHECK-NEXT: br i1 true, label [[FIRST:%.*]], label [[TEST1]]
+; CHECK: first:
+; CHECK-NEXT: ret void
+;
+;
+; CHECK-LABEL: @function2(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[E_LOC:%.*]] = alloca i32, align 4
+; CHECK-NEXT: [[TMP0:%.*]] = alloca i32, align 4
+; CHECK-NEXT: [[C:%.*]] = load i32, i32* [[TMP0]], align 4
+; CHECK-NEXT: [[Y:%.*]] = mul i32 [[C]], [[C]]
+; CHECK-NEXT: br label [[TEST1:%.*]]
+; CHECK: dummy:
+; CHECK-NEXT: ret void
+; CHECK: test1:
+; CHECK-NEXT: [[TMP1:%.*]] = phi i32 [ [[E_RELOAD:%.*]], [[TEST1]] ], [ [[Y]], [[ENTRY:%.*]] ]
+; CHECK-NEXT: [[TMP2:%.*]] = phi i32 [ [[Y]], [[ENTRY]] ], [ [[E_RELOAD]], [[TEST1]] ]
+; CHECK-NEXT: [[LT_CAST:%.*]] = bitcast i32* [[E_LOC]] to i8*
+; CHECK-NEXT: call void @llvm.lifetime.start.p0i8(i64 -1, i8* [[LT_CAST]])
+; CHECK-NEXT: call void @outlined_ir_func_0(i32* [[TMP0]], i32 [[C]], i32* [[E_LOC]])
+; CHECK-NEXT: [[E_RELOAD]] = load i32, i32* [[E_LOC]], align 4
+; CHECK-NEXT: call void @llvm.lifetime.end.p0i8(i64 -1, i8* [[LT_CAST]])
+; CHECK-NEXT: [[TMP3:%.*]] = mul i32 [[C]], [[C]]
+; CHECK-NEXT: br i1 true, label [[FIRST:%.*]], label [[TEST1]]
+; CHECK: first:
+; CHECK-NEXT: ret void
+;
+;
+; CHECK-LABEL: define internal void @outlined_ir_func_0(
+; CHECK-NEXT: newFuncRoot:
+; CHECK-NEXT: br label [[TEST1_TO_OUTLINE:%.*]]
+; CHECK: test1_to_outline:
+; CHECK-NEXT: [[E:%.*]] = load i32, i32* [[TMP0:%.*]], align 4
+; CHECK-NEXT: [[TMP3:%.*]] = add i32 [[TMP1:%.*]], [[TMP1]]
+; CHECK-NEXT: br label [[TEST1_AFTER_OUTLINE_EXITSTUB:%.*]]
+; CHECK: test1_after_outline.exitStub:
+; CHECK-NEXT: store i32 [[E]], i32* [[TMP2:%.*]], align 4
+; CHECK-NEXT: ret void
+;
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