[PowerPC] Change liveness testing in VSX FMA mutation pass

With VSX enabled, LLVM crashes when compiling
test/CodeGen/PowerPC/fma.ll.  I traced this to the liveness test
that's revised in this patch. The interval test is designed to only
work for virtual registers, but in this case the AddendSrcReg is
physical. Since there is already a walk of the MIs between the
AddendMI and the FMA, I added a check for def/kill of the AddendSrcReg
in that loop.  At Hal Finkel's request, I converted the liveness test
to an assert restricted to virtual registers.

I've changed the fma.ll test to have VSX and non-VSX variants so we
can test both kinds of multiply-adds.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220090 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/PowerPC/PPCInstrInfo.cpp b/lib/Target/PowerPC/PPCInstrInfo.cpp
index 61adc4b30e0a67600e0ce6bae5781204b84b8f16..3b0f1efbd02ac449adb10f392620cbf5d19408e2 100644 (file)
--- a/lib/Target/PowerPC/PPCInstrInfo.cpp
+++ b/lib/Target/PowerPC/PPCInstrInfo.cpp
@@ -1622,6 +1622,7 @@ protected:
       bool Changed = false;
 
       MachineRegisterInfo &MRI = MBB.getParent()->getRegInfo();
+      const TargetRegisterInfo *TRI = &TII->getRegisterInfo();
       for (MachineBasicBlock::iterator I = MBB.begin(), IE = MBB.end();
            I != IE; ++I) {
         MachineInstr *MI = I;
@@ -1687,16 +1688,26 @@ protected:
         // In theory, there could be other uses of the addend copy before this
         // fma.  We could deal with this, but that would require additional
         // logic below and I suspect it will not occur in any relevant
-        // situations.
-        bool OtherUsers = false;
+        // situations.  Additionally, check whether the copy source is killed
+        // prior to the fma.  In order to replace the addend here with the
+        // source of the copy, it must still be live here.  We can't use
+        // interval testing for a physical register, so as long as we're
+        // walking the MIs we may as well test liveness here.
+        bool OtherUsers = false, KillsAddendSrc = false;
         for (auto J = std::prev(I), JE = MachineBasicBlock::iterator(AddendMI);
-             J != JE; --J)
+             J != JE; --J) {
           if (J->readsVirtualRegister(AddendMI->getOperand(0).getReg())) {
             OtherUsers = true;
             break;
           }
+          if (J->modifiesRegister(AddendSrcReg, TRI) ||
+              J->killsRegister(AddendSrcReg, TRI)) {
+            KillsAddendSrc = true;
+            break;
+          }
+        }
 
-        if (OtherUsers)
+        if (OtherUsers || KillsAddendSrc)
           continue;
 
         // Find one of the product operands that is killed by this instruction.
@@ -1717,10 +1728,11 @@ protected:
         if (!KilledProdOp)
           continue;
 
-        // In order to replace the addend here with the source of the copy,
-        // it must still be live here.
-        if (!LIS->getInterval(AddendMI->getOperand(1).getReg()).liveAt(FMAIdx))
-          continue;
+        // For virtual registers, verify that the addend source register
+        // is live here (as should have been assured above).
+        if (TargetRegisterInfo::isVirtualRegister(AddendSrcReg))
+          assert(LIS->getInterval(AddendSrcReg).liveAt(FMAIdx) &&
+                 "Addend source register is not available!");
 
         // Transform: (O2 * O3) + O1 -> (O2 * O1) + O3.
 

diff --git a/test/CodeGen/PowerPC/fma.ll b/test/CodeGen/PowerPC/fma.ll
index 6bef3acf64b5d02c5b8780420abf800a914fa69b..270c141fa91c8167700fd00362994a0954db926b 100644 (file)
--- a/test/CodeGen/PowerPC/fma.ll
+++ b/test/CodeGen/PowerPC/fma.ll
@@ -1,4 +1,5 @@
-; RUN: llc < %s -march=ppc32 -fp-contract=fast | FileCheck %s
+; RUN: llc < %s -march=ppc32 -fp-contract=fast -mattr=-vsx | FileCheck %s
+; RUN: llc < %s -mtriple=powerpc64-unknown-linux-gnu -fp-contract=fast -mattr=+vsx | FileCheck -check-prefix=CHECK-VSX %s
 
 declare double @dummy1(double) #0
 declare double @dummy2(double, double) #0
@@ -11,6 +12,10 @@ define double @test_FMADD1(double %A, double %B, double %C) {
 ; CHECK-LABEL: test_FMADD1:
 ; CHECK: fmadd
 ; CHECK-NEXT: blr
+
+; CHECK-VSX-LABEL: test_FMADD1:
+; CHECK-VSX: xsmaddmdp
+; CHECK-VSX-NEXT: blr
 }
 
 define double @test_FMADD2(double %A, double %B, double %C) {
@@ -20,6 +25,10 @@ define double @test_FMADD2(double %A, double %B, double %C) {
 ; CHECK-LABEL: test_FMADD2:
 ; CHECK: fmadd
 ; CHECK-NEXT: blr
+
+; CHECK-VSX-LABEL: test_FMADD2:
+; CHECK-VSX: xsmaddmdp
+; CHECK-VSX-NEXT: blr
 }
 
 define double @test_FMSUB1(double %A, double %B, double %C) {
@@ -29,6 +38,10 @@ define double @test_FMSUB1(double %A, double %B, double %C) {
 ; CHECK-LABEL: test_FMSUB1:
 ; CHECK: fmsub
 ; CHECK-NEXT: blr
+
+; CHECK-VSX-LABEL: test_FMSUB1:
+; CHECK-VSX: xsmsubmdp
+; CHECK-VSX-NEXT: blr
 }
 
 define double @test_FMSUB2(double %A, double %B, double %C, double %D) {
@@ -40,6 +53,10 @@ define double @test_FMSUB2(double %A, double %B, double %C, double %D) {
 ; CHECK-LABEL: test_FMSUB2:
 ; CHECK: fmadd
 ; CHECK-NEXT: fmsub
+
+; CHECK-VSX-LABEL: test_FMSUB2:
+; CHECK-VSX: xsmaddadp
+; CHECK-VSX-NEXT: xsmsubmdp
 }
 
 define double @test_FNMADD1(double %A, double %B, double %C) {
@@ -50,6 +67,10 @@ define double @test_FNMADD1(double %A, double %B, double %C) {
 ; CHECK-LABEL: test_FNMADD1:
 ; CHECK: fnmadd
 ; CHECK-NEXT: blr
+
+; CHECK-VSX-LABEL: test_FNMADD1:
+; CHECK-VSX: xsnmaddmdp
+; CHECK-VSX-NEXT: blr
 }
 
 define double @test_FNMADD2(double %A, double %B, double %C) {
@@ -60,6 +81,10 @@ define double @test_FNMADD2(double %A, double %B, double %C) {
 ; CHECK-LABEL: test_FNMADD2:
 ; CHECK: fnmadd
 ; CHECK-NEXT: blr
+
+; CHECK-VSX-LABEL: test_FNMADD2:
+; CHECK-VSX: xsnmaddmdp
+; CHECK-VSX-NEXT: blr
 }
 
 define double @test_FNMSUB1(double %A, double %B, double %C) {
@@ -69,6 +94,9 @@ define double @test_FNMSUB1(double %A, double %B, double %C) {
 ; CHECK-LABEL: test_FNMSUB1:
 ; CHECK: fnmsub
 ; CHECK-NEXT: blr
+
+; CHECK-VSX-LABEL: test_FNMSUB1:
+; CHECK-VSX: xsnmsubmdp
 }
 
 define double @test_FNMSUB2(double %A, double %B, double %C) {
@@ -79,6 +107,10 @@ define double @test_FNMSUB2(double %A, double %B, double %C) {
 ; CHECK-LABEL: test_FNMSUB2:
 ; CHECK: fnmsub
 ; CHECK-NEXT: blr
+
+; CHECK-VSX-LABEL: test_FNMSUB2:
+; CHECK-VSX: xsnmsubmdp
+; CHECK-VSX-NEXT: blr
 }
 
 define float @test_FNMSUBS(float %A, float %B, float %C) {
@@ -89,4 +121,8 @@ define float @test_FNMSUBS(float %A, float %B, float %C) {
 ; CHECK-LABEL: test_FNMSUBS:
 ; CHECK: fnmsubs
 ; CHECK-NEXT: blr
+
+; CHECK-VSX-LABEL: test_FNMSUBS:
+; CHECK-VSX: fnmsubs
+; CHECK-VSX-NEXT: blr
 }