Fix the PPC subsumes-predicate check

For one predicate to subsume another, they must both check the same condition
register. Failure to check this prerequisite was causing miscompiles.

Fixes PR18003.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@197089 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/PowerPC/PPCInstrInfo.cpp b/lib/Target/PowerPC/PPCInstrInfo.cpp
index bdeb649d2206d02583d1b42c3b88bd6f2b991005..c4582c540ba3f3b9b7e12236da7c00349541a255 100644 (file)
--- a/lib/Target/PowerPC/PPCInstrInfo.cpp
+++ b/lib/Target/PowerPC/PPCInstrInfo.cpp
@@ -988,6 +988,10 @@ bool PPCInstrInfo::SubsumesPredicate(
   if (Pred2[1].getReg() == PPC::CTR8 || Pred2[1].getReg() == PPC::CTR)
     return false;
 
+  // P1 can only subsume P2 if they test the same condition register.
+  if (Pred1[1].getReg() != Pred2[1].getReg())
+    return false;
+
   PPC::Predicate P1 = (PPC::Predicate) Pred1[0].getImm();
   PPC::Predicate P2 = (PPC::Predicate) Pred2[0].getImm();
 

diff --git a/test/CodeGen/PowerPC/subsumes-pred-regs.ll b/test/CodeGen/PowerPC/subsumes-pred-regs.ll
new file mode 100644 (file)
index 0000000..97ac788
--- /dev/null
+++ b/test/CodeGen/PowerPC/subsumes-pred-regs.ll
@@ -0,0 +1,65 @@
+; RUN: llc < %s -mcpu=ppc64 | FileCheck %s
+target datalayout = "E-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-f128:128:128-v128:128:128-n32:64"
+target triple = "powerpc64-unknown-linux-gnu"
+
+; Function Attrs: nounwind
+define zeroext i1 @test1() unnamed_addr #0 align 2 {
+
+; CHECK-LABEL: @test1
+
+entry:
+  br i1 undef, label %lor.end, label %lor.rhs
+
+lor.rhs:                                          ; preds = %entry
+  unreachable
+
+lor.end:                                          ; preds = %entry
+  br i1 undef, label %land.rhs, label %if.then
+
+if.then:                                          ; preds = %lor.end
+  br i1 undef, label %return, label %if.end.i24
+
+if.end.i24:                                       ; preds = %if.then
+  %0 = load i32* undef, align 4
+  %lnot.i.i16.i23 = icmp eq i32 %0, 0
+  br i1 %lnot.i.i16.i23, label %if.end7.i37, label %test.exit27.i34
+
+test.exit27.i34: ; preds = %if.end.i24
+  br i1 undef, label %return, label %if.end7.i37
+
+if.end7.i37:                                      ; preds = %test.exit27.i34, %if.end.i24
+  %tobool.i.i36 = icmp eq i8 undef, 0
+  br i1 %tobool.i.i36, label %return, label %if.then9.i39
+
+if.then9.i39:                                     ; preds = %if.end7.i37
+  br i1 %lnot.i.i16.i23, label %return, label %lor.rhs.i.i49
+
+; CHECK: .LBB0_7:
+; CHECK:       beq 1, .LBB0_10
+; CHECK:       beq 0, .LBB0_10
+; CHECK: .LBB0_9:
+
+lor.rhs.i.i49:                                    ; preds = %if.then9.i39
+  %cmp.i.i.i.i48 = icmp ne i64 undef, 0
+  br label %return
+
+land.rhs:                                         ; preds = %lor.end
+  br i1 undef, label %return, label %if.end.i
+
+if.end.i:                                         ; preds = %land.rhs
+  br i1 undef, label %return, label %if.then9.i
+
+if.then9.i:                                       ; preds = %if.end.i
+  br i1 undef, label %return, label %lor.rhs.i.i
+
+lor.rhs.i.i:                                      ; preds = %if.then9.i
+  %cmp.i.i.i.i = icmp ne i64 undef, 0
+  br label %return
+
+return:                                           ; preds = %lor.rhs.i.i, %if.then9.i, %if.end.i, %land.rhs, %lor.rhs.i.i49, %if.then9.i39, %if.end7.i37, %test.exit27.i34, %if.then
+  %retval.0 = phi i1 [ false, %if.then ], [ false, %test.exit27.i34 ], [ true, %if.end7.i37 ], [ true, %if.then9.i39 ], [ %cmp.i.i.i.i48, %lor.rhs.i.i49 ], [ false, %land.rhs ], [ true, %if.end.i ], [ true, %if.then9.i ], [ %cmp.i.i.i.i, %lor.rhs.i.i ]
+  ret i1 %retval.0
+}
+
+attributes #0 = { nounwind }
+