Fix IfConverter to handle regmask machine operands.

Note, this is a recommit of r236515 after fixing an error in r236514.  The buildbot ran fast enough that it picked up r236514 prior to r236515 and threw an error.  r236515 itself ran 'make check' without errors.

Original commit message follows:

A regmask (typically seen on a call) clobbers the set of registers it lists.  The IfConverter, in UpdatePredRedefs, was handling register defs, but not regmasks.

These are slightly different to a def in that we need to add both an implicit use and def to appease the machine verifier.  Otherwise, uses after the if converted call could think they are reading an undefined register.

Reviewed by Matthias Braun and Quentin Colombet.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@236550 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/IfConversion.cpp b/lib/CodeGen/IfConversion.cpp
index 6359d765da4c62cb56dfb1584e0299bb0f67638e..3ac78b258540db94132c38796aee8cb6dafefa65 100644 (file)
--- a/lib/CodeGen/IfConversion.cpp
+++ b/lib/CodeGen/IfConversion.cpp
@@ -985,8 +985,21 @@ static void UpdatePredRedefs(MachineInstr *MI, LivePhysRegs &Redefs) {
     // take a mutable instruction instead of const.
     MachineInstr *OpMI = const_cast<MachineInstr*>(Op.getParent());
     MachineInstrBuilder MIB(*OpMI->getParent()->getParent(), OpMI);
-    if (Op.isReg())
+    if (Op.isRegMask()) {
+      // First handle regmasks.  They clobber any entries in the mask which
+      // means that we need a def for those registers.
       MIB.addReg(Reg.first, RegState::Implicit | RegState::Undef);
+
+      // We also need to add an implicit def of this register for the later
+      // use to read from.
+      // For the register allocator to have allocated a register clobbered
+      // by the call which is used later, it must be the case that
+      // the call doesn't return.
+      MIB.addReg(Reg.first, RegState::Implicit | RegState::Define);
+      continue;
+    }
+    assert(Op.isReg() && "Register operand required");
+    MIB.addReg(Reg.first, RegState::Implicit | RegState::Undef);
   }
 }
 

diff --git a/test/CodeGen/ARM/ifcvt-regmask-noreturn.ll b/test/CodeGen/ARM/ifcvt-regmask-noreturn.ll
new file mode 100644 (file)
index 0000000..cf04fc9
--- /dev/null
+++ b/test/CodeGen/ARM/ifcvt-regmask-noreturn.ll
@@ -0,0 +1,45 @@
+; RUN: llc %s -o - -verify-machineinstrs | FileCheck %s
+
+target datalayout = "e-m:o-p:32:32-f64:32:64-v64:32:64-v128:32:128-a:0:32-n32-S32"
+target triple = "thumbv7s-apple-ios8.0.0"
+
+@debw = external global i8*, align 4
+
+; This test ensures that the stack_chk call correctly puts implicit uses/defs for the regsiters
+; live across it when if converting.  This will be R0 which is passed to the call to free at the end
+; of the function.
+; Prior to this change, the stack_chk call (which does not return) would clobber R0 in its regmask,
+; leading to verifier errors because the later use of R0 in free() is not live.
+
+; CHECK-LABEL: @test
+; CHECK: stack_chk_fail
+
+; Function Attrs: ssp
+define void @test(i32 %argc, i8** nocapture readonly %argv, i32* %ptr, i32 %val) #0 {
+entry:
+  %count.i = alloca [256 x i32], align 4
+  %cmp284.i = icmp eq i32 %val, 0
+  br i1 %cmp284.i, label %for.end31.i, label %for.body21.i
+
+for.body21.i:                                     ; preds = %entry
+  %arrayidx23.i = getelementptr inbounds [256 x i32], [256 x i32]* %count.i, i32 0, i32 1
+  %tmp20 = load i32, i32* %arrayidx23.i, align 4, !tbaa !0
+  store i32 %tmp20, i32* %ptr, align 4, !tbaa !0
+  br label %for.end31.i
+
+for.end31.i:                                      ; preds = %for.body21.i, %entry
+  %tmp21 = load i8*, i8** @debw, align 4, !tbaa !4
+  tail call void @free(i8* %tmp21)
+  ret void
+}
+
+declare void @free(i8* nocapture)
+
+attributes #0 = { ssp "stack-protector-buffer-size"="8" }
+
+!0 = !{!1, !1, i64 0}
+!1 = !{!"int", !2, i64 0}
+!2 = !{!"omnipotent char", !3, i64 0}
+!3 = !{!"Simple C/C++ TBAA"}
+!4 = !{!5, !5, i64 0}
+!5 = !{!"any pointer", !2, i64 0}