Correctly vectorize powi.

The powi intrinsic requires special handling because it always takes a single
integer power regardless of the result type. As a result, we can vectorize
only if the powers are equal. Fixes PR12364.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@153797 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Transforms/Vectorize/BBVectorize.cpp

@@ -647,6 +647,20 @@ namespace {
       // FIXME: We may want to vectorize non-constant shuffles also.
     }
 
+    // The powi intrinsic is special because only the first argument is
+    // vectorized, the second arguments must be equal.
+    CallInst *CI = dyn_cast<CallInst>(I);
+    Function *FI;
+    if (CI && (FI = CI->getCalledFunction()) &&
+        FI->getIntrinsicID() == Intrinsic::powi) {
+
+      Value *A1I = CI->getArgOperand(1),
+            *A1J = cast<CallInst>(J)->getArgOperand(1);
+      const SCEV *A1ISCEV = SE->getSCEV(A1I),
+                 *A1JSCEV = SE->getSCEV(A1J);
+      return (A1ISCEV == A1JSCEV);
+    }
+
     return true;
   }
 
@@ -1518,9 +1532,10 @@ namespace {
         ReplacedOperands[o] = getReplacementPointerInput(Context, I, J, o,
                                 FlipMemInputs);
         continue;
-      } else if (isa<CallInst>(I) && o == NumOperands-1) {
+      } else if (isa<CallInst>(I)) {
         Function *F = cast<CallInst>(I)->getCalledFunction();
         unsigned IID = F->getIntrinsicID();
+        if (o == NumOperands-1) {
           BasicBlock &BB = *I->getParent();
   
           Module *M = BB.getParent()->getParent();
@@ -1531,6 +1546,13 @@ namespace {
           ReplacedOperands[o] = Intrinsic::getDeclaration(M,
             (Intrinsic::ID) IID, VArgType);
           continue;
+        } else if (IID == Intrinsic::powi && o == 1) {
+          // The second argument of powi is a single integer and we've already
+          // checked that both arguments are equal. As a result, we just keep
+          // I's second argument.
+          ReplacedOperands[o] = I->getOperand(o);
+          continue;
+        }
       } else if (isa<ShuffleVectorInst>(I) && o == NumOperands-1) {
         ReplacedOperands[o] = getReplacementShuffleMask(Context, I, J);
         continue;

test/Transforms/BBVectorize/simple-int.ll

@@ -3,6 +3,7 @@ target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f3
 
 declare double @llvm.fma.f64(double, double, double)
 declare double @llvm.cos.f64(double)
+declare double @llvm.powi.f64(double, i32)
 
 ; Basic depth-3 chain with fma
 define double @test1(double %A1, double %A2, double %B1, double %B2, double %C1, double %C2) {
@@ -54,6 +55,49 @@ define double @test2(double %A1, double %A2, double %B1, double %B2) {
 ; CHECK: ret double %R
 }
 
+; Basic depth-3 chain with powi
+define double @test3(double %A1, double %A2, double %B1, double %B2, i32 %P) {
+
+	%X1 = fsub double %A1, %B1
+	%X2 = fsub double %A2, %B2
+	%Y1 = call double @llvm.powi.f64(double %X1, i32 %P)
+	%Y2 = call double @llvm.powi.f64(double %X2, i32 %P)
+	%Z1 = fadd double %Y1, %B1
+	%Z2 = fadd double %Y2, %B2
+	%R  = fmul double %Z1, %Z2
+	ret double %R
+; CHECK: @test3
+; CHECK: %X1.v.i1.1 = insertelement <2 x double> undef, double %B1, i32 0
+; CHECK: %X1.v.i0.1 = insertelement <2 x double> undef, double %A1, i32 0
+; CHECK: %X1.v.i1.2 = insertelement <2 x double> %X1.v.i1.1, double %B2, i32 1
+; CHECK: %X1.v.i0.2 = insertelement <2 x double> %X1.v.i0.1, double %A2, i32 1
+; CHECK: %X1 = fsub <2 x double> %X1.v.i0.2, %X1.v.i1.2
+; CHECK: %Y1 = call <2 x double> @llvm.powi.v2f64(<2 x double> %X1, i32 %P)
+; CHECK: %Z1 = fadd <2 x double> %Y1, %X1.v.i1.2
+; CHECK: %Z1.v.r1 = extractelement <2 x double> %Z1, i32 0
+; CHECK: %Z1.v.r2 = extractelement <2 x double> %Z1, i32 1
+; CHECK: %R = fmul double %Z1.v.r1, %Z1.v.r2
+; CHECK: ret double %R
+}
+
+; Basic depth-3 chain with powi (different powers: should not vectorize)
+define double @test4(double %A1, double %A2, double %B1, double %B2, i32 %P) {
+
+	%X1 = fsub double %A1, %B1
+	%X2 = fsub double %A2, %B2
+        %P2 = add i32 %P, 1
+	%Y1 = call double @llvm.powi.f64(double %X1, i32 %P)
+	%Y2 = call double @llvm.powi.f64(double %X2, i32 %P2)
+	%Z1 = fadd double %Y1, %B1
+	%Z2 = fadd double %Y2, %B2
+	%R  = fmul double %Z1, %Z2
+	ret double %R
+; CHECK: @test4
+; CHECK-NOT: <2 x double>
+; CHECK: ret double %R
+}
+
 ; CHECK: declare <2 x double> @llvm.fma.v2f64(<2 x double>, <2 x double>, <2 x double>) nounwind readnone
 ; CHECK: declare <2 x double> @llvm.cos.v2f64(<2 x double>) nounwind readonly
+; CHECK: declare <2 x double> @llvm.powi.v2f64(<2 x double>, i32) nounwind readonly