guix/gnu/packages/patches/llvm-9-fix-lpad-miscompilation.patch

From 011fb5bf8b31316472fccb1a19c91912246df9b2 Mon Sep 17 00:00:00 2001
From: Reid Kleckner <rnk@google.com>
Date: Sat, 28 Mar 2020 11:03:14 -0700
Subject: [PATCH] [CodeGen] Fix sinking local values in lpads with phis

There was already a test case for landingpads to handle this case, but I
had forgotten to consider PHI instructions preceding the EH_LABEL in the
landingpad.

PR45261
---
 llvm/lib/CodeGen/SelectionDAG/FastISel.cpp | 17 +++++++++-
 llvm/test/CodeGen/X86/sink-local-value.ll  | 36 ++++++++++++++++++++++
 2 files changed, 52 insertions(+), 1 deletion(-)

diff --git a/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp b/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
index 5ac3606dc662..2638b1e8a05c 100644
--- a/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
@@ -225,6 +225,21 @@ static bool isRegUsedByPhiNodes(unsigned DefReg,
   return false;
 }
 
+static bool isTerminatingEHLabel(MachineBasicBlock *MBB, MachineInstr &MI) {
+  // Ignore non-EH labels.
+  if (!MI.isEHLabel())
+    return false;
+
+  // Any EH label outside a landing pad must be for an invoke. Consider it a
+  // terminator.
+  if (!MBB->isEHPad())
+    return true;
+
+  // If this is a landingpad, the first non-phi instruction will be an EH_LABEL.
+  // Don't consider that label to be a terminator.
+  return MI.getIterator() != MBB->getFirstNonPHI();
+}
+
 /// Build a map of instruction orders. Return the first terminator and its
 /// order. Consider EH_LABEL instructions to be terminators as well, since local
 /// values for phis after invokes must be materialized before the call.
@@ -233,7 +248,7 @@ void FastISel::InstOrderMap::initialize(
   unsigned Order = 0;
   for (MachineInstr &I : *MBB) {
     if (!FirstTerminator &&
-        (I.isTerminator() || (I.isEHLabel() && &I != &MBB->front()))) {
+        (I.isTerminator() || isTerminatingEHLabel(MBB, I))) {
       FirstTerminator = &I;
       FirstTerminatorOrder = Order;
     }
diff --git a/llvm/test/CodeGen/X86/sink-local-value.ll b/llvm/test/CodeGen/X86/sink-local-value.ll
index b0e511ac1189..f7d861ac9b6c 100644
--- a/llvm/test/CodeGen/X86/sink-local-value.ll
+++ b/llvm/test/CodeGen/X86/sink-local-value.ll
@@ -145,6 +145,42 @@ try.cont:                                         ; preds = %entry, %lpad
 ; CHECK:         retl
 
 
+define i32 @lpad_phi() personality i32 (...)* @__gxx_personality_v0 {
+entry:
+  store i32 42, i32* @sink_across
+  invoke void @may_throw()
+          to label %try.cont unwind label %lpad
+
+lpad:                                             ; preds = %entry
+  %p = phi i32 [ 11, %entry ]  ; Trivial, but -O0 keeps it
+  %0 = landingpad { i8*, i32 }
+          catch i8* null
+  store i32 %p, i32* @sink_across
+  br label %try.cont
+
+try.cont:                                         ; preds = %entry, %lpad
+  %r.0 = phi i32 [ 13, %entry ], [ 55, %lpad ]
+  ret i32 %r.0
+}
+
+; The constant materialization should be *after* the stores to sink_across, but
+; before any EH_LABEL.
+
+; CHECK-LABEL: lpad_phi:
+; CHECK:         movl    $42, sink_across
+; CHECK:         movl    $13, %{{[a-z]*}}
+; CHECK: .Ltmp{{.*}}:
+; CHECK:         calll   may_throw
+; CHECK: .Ltmp{{.*}}:
+; CHECK:         jmp     .LBB{{.*}}
+; CHECK: .LBB{{.*}}:                                # %lpad
+; CHECK-NEXT: .Ltmp{{.*}}:
+; CHECK:         movl    {{.*}}, sink_across
+; CHECK:         movl    $55, %{{[a-z]*}}
+; CHECK: .LBB{{.*}}:                                # %try.cont
+; CHECK:         retl
+
+
 ; Function Attrs: nounwind readnone speculatable
 declare void @llvm.dbg.value(metadata, metadata, metadata) #0