[PowerPC] Avoid VSX FMA mutate when killed product reg = addend reg

With VSX enabled, test/CodeGen/PowerPC/recipest.ll exposes a bug in
the FMA mutation pass.  If we have a situation where a killed product
register is the same register as the FMA target, such as:

   %vreg5<def,tied1> = XSNMSUBADP %vreg5<tied0>, %vreg11, %vreg5,
                       %RM<imp-use>; VSFRC:%vreg5 F8RC:%vreg11

then the substitution makes no sense.  We end up getting a crash when
we try to extend the interval associated with the killed product
register, as there is already a live range for %vreg5 there.  This
patch just disables the mutation under those circumstances.

Since recipest.ll generates different code with VMX enabled, I've
modified that test to use -mattr=-vsx.  I've borrowed the code from
that test that exposed the bug and placed it in fma-mutate.ll, where
it tests several mutation opportunities including the "bad" one.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220290 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/PowerPC/PPCInstrInfo.cpp b/lib/Target/PowerPC/PPCInstrInfo.cpp
index ff2633eac3f874e2bfafcb3e84eb5a0519f33f82..daf8790fefcc5988e1c7d879f1f5bcf78af78beb 100644 (file)
--- a/lib/Target/PowerPC/PPCInstrInfo.cpp
+++ b/lib/Target/PowerPC/PPCInstrInfo.cpp
@@ -1754,6 +1754,12 @@ protected:
 
         unsigned OldFMAReg = MI->getOperand(0).getReg();
 
 
         unsigned OldFMAReg = MI->getOperand(0).getReg();
 

+        // The transformation doesn't work well with things like:
+        //    %vreg5 = A-form-op %vreg5, %vreg11, %vreg5;
+        // so leave such things alone.
+        if (OldFMAReg == KilledProdReg)
+          continue;
+

         assert(OldFMAReg == AddendMI->getOperand(0).getReg() &&
                "Addend copy not tied to old FMA output!");
 
         assert(OldFMAReg == AddendMI->getOperand(0).getReg() &&
                "Addend copy not tied to old FMA output!");
 

diff --git a/test/CodeGen/PowerPC/fma-mutate.ll b/test/CodeGen/PowerPC/fma-mutate.ll
new file mode 100644 (file)
index 0000000..1a391f4
--- /dev/null
+++ b/test/CodeGen/PowerPC/fma-mutate.ll
@@ -0,0 +1,21 @@
+; Test several VSX FMA mutation opportunities.  The first one isn't a
+; reasonable transformation because the killed product register is the
+; same as the FMA target register.  The second one is legal.  The third
+; one doesn't fit the feeding-copy pattern.
+
+; RUN: llc < %s -mtriple=powerpc64-unknown-linux-gnu -mcpu=pwr7 -enable-unsafe-fp-math -mattr=+vsx | 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"
+
+declare double @llvm.sqrt.f64(double)
+
+define double @foo3(double %a) nounwind {
+  %r = call double @llvm.sqrt.f64(double %a)
+  ret double %r
+
+; CHECK: @foo3
+; CHECK: xsnmsubadp [[REG:[0-9]+]], {{[0-9]+}}, [[REG]]
+; CHECK: xsmaddmdp
+; CHECK: xsmaddadp
+}
+

diff --git a/test/CodeGen/PowerPC/recipest.ll b/test/CodeGen/PowerPC/recipest.ll
index 2f6a3eca48829731f4bf91d71ed87a6f890ffe87..cd77548b281bf499366bf7218efcd32fb6737826 100644 (file)
--- a/test/CodeGen/PowerPC/recipest.ll
+++ b/test/CodeGen/PowerPC/recipest.ll
@@ -1,5 +1,5 @@
-; RUN: llc < %s -mtriple=powerpc64-unknown-linux-gnu -mcpu=pwr7 -enable-unsafe-fp-math | FileCheck %s
-; RUN: llc < %s -mtriple=powerpc64-unknown-linux-gnu -mcpu=pwr7 | FileCheck -check-prefix=CHECK-SAFE %s
+; RUN: llc < %s -mtriple=powerpc64-unknown-linux-gnu -mcpu=pwr7 -enable-unsafe-fp-math -mattr=-vsx | FileCheck %s
+; RUN: llc < %s -mtriple=powerpc64-unknown-linux-gnu -mcpu=pwr7 -mattr=-vsx | FileCheck -check-prefix=CHECK-SAFE %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"
 
 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"