From: Tim Northover <tnorthover@apple.com>
Date: Mon, 5 Dec 2016 23:10:19 +0000 (+0000)
Subject: GlobalISel: avoid looking too closely at PHIs when we bail.
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=416ccca7e07c3f06fa45f4c9d4365a3687fc1748;p=llvm

GlobalISel: avoid looking too closely at PHIs when we bail.

The function used to finish off PHIs by adding the relevant basic blocks can
fail if we're aborting and still don't actually have the needed
MachineBasicBlocks. So avoid trying in that case.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@288727 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/CodeGen/GlobalISel/IRTranslator.cpp b/lib/CodeGen/GlobalISel/IRTranslator.cpp
index 68fec1a555f..c986e65049f 100644
--- a/lib/CodeGen/GlobalISel/IRTranslator.cpp
+++ b/lib/CodeGen/GlobalISel/IRTranslator.cpp
@@ -678,8 +678,6 @@ void IRTranslator::finishPendingPhis() {
       MIB.addMBB(BBToMBB[PI->getIncomingBlock(i)]);
     }
   }
-
-  PendingPHIs.clear();
 }
 
 bool IRTranslator::translate(const Instruction &Inst) {
@@ -725,10 +723,9 @@ bool IRTranslator::translate(const Constant &C, unsigned Reg) {
 }
 
 void IRTranslator::finalizeFunction() {
-  finishPendingPhis();
-
   // Release the memory used by the different maps we
   // needed during the translation.
+  PendingPHIs.clear();
   ValToVReg.clear();
   FrameIndices.clear();
   Constants.clear();
@@ -758,6 +755,7 @@ bool IRTranslator::runOnMachineFunction(MachineFunction &MF) {
     if (!TPC->isGlobalISelAbortEnabled()) {
       MIRBuilder.getMF().getProperties().set(
           MachineFunctionProperties::Property::FailedISel);
+      finalizeFunction();
       return false;
     }
     report_fatal_error("Unable to lower arguments");
@@ -777,7 +775,7 @@ bool IRTranslator::runOnMachineFunction(MachineFunction &MF) {
     MIRBuilder.setMBB(MBB);
 
     for (const Instruction &Inst: BB) {
-      bool Succeeded = translate(Inst);
+      Succeeded &= translate(Inst);
       if (!Succeeded) {
         if (TPC->isGlobalISelAbortEnabled())
           reportTranslationError(Inst, "unable to translate instruction");
@@ -787,11 +785,15 @@ bool IRTranslator::runOnMachineFunction(MachineFunction &MF) {
     }
   }
 
-  finalizeFunction();
+  if (Succeeded) {
+    finishPendingPhis();
+
+    // Now that the MachineFrameInfo has been configured, no further changes to
+    // the reserved registers are possible.
+    MRI->freezeReservedRegs(MF);
+  }
 
-  // Now that the MachineFrameInfo has been configured, no further changes to
-  // the reserved registers are possible.
-  MRI->freezeReservedRegs(MF);
+  finalizeFunction();
 
   return false;
 }
diff --git a/test/CodeGen/AArch64/GlobalISel/arm64-fallback.ll b/test/CodeGen/AArch64/GlobalISel/arm64-fallback.ll
index 25d6c1f191c..e7b1f04e03b 100644
--- a/test/CodeGen/AArch64/GlobalISel/arm64-fallback.ll
+++ b/test/CodeGen/AArch64/GlobalISel/arm64-fallback.ll
@@ -36,4 +36,24 @@ define i128 @ABIi128(i128 %arg1) {
 ; FALLBACK-WITH-REPORT-OUT: fmov d0, #1.0
 define [1 x double] @constant() {
   ret [1 x double] [double 1.0]
+}
+
+  ; The key problem here is that we may fail to create an MBB referenced by a
+  ; PHI. If so, we cannot complete the G_PHI and mustn't try or bad things
+  ; happen.
+; FALLBACK-WITH-REPORT-ERR: warning: Instruction selection used fallback path for pending_phis
+define i32 @pending_phis(i1 %tst, i32 %val, i32* %addr) {
+  br i1 %tst, label %true, label %false
+
+end:
+  %res = phi i32 [%val, %true], [42, %false]
+  ret i32 %res
+
+true:
+  store atomic i32 42, i32* %addr seq_cst, align 4
+  br label %end
+
+false:
+  br label %end
+
 }