[llvm] PreISelIntrinsicLowering: Lower llvm.exp to a loop if scalable vec arg (PR #117568)

[Matt Arsenault via llvm-commits]

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@@ -0,0 +1,23 @@
+; RUN: opt -passes=pre-isel-intrinsic-lowering -S < %s | FileCheck %s
+
+define <vscale x 4 x float> @softmax_kernel() {
+; CHECK-LABEL: define <vscale x 4 x float> @softmax_kernel(
+; CHECK-NEXT:    [[VSCALE:%.*]] = call i64 @llvm.vscale.i64()
+; CHECK-NEXT:    [[LOOPEND:%.*]] = mul i64 [[VSCALE]], 4
+; CHECK-NEXT:    br label %[[LOOPBODY:.*]]
+; CHECK:       [[LOOPBODY]]:
+; CHECK-NEXT:    [[IDX:%.*]] = phi i64 [ 0, %0 ], [ [[NEW_IDX:%.*]], %[[LOOPBODY]] ]
+; CHECK-NEXT:    [[VEC:%.*]] = phi <vscale x 4 x float> [ zeroinitializer, %0 ], [ [[NEW_VEC:.*]], %[[LOOPBODY]] ]
+; CHECK-NEXT:    [[ELEM:%.*]] = extractelement <vscale x 4 x float> [[VEC]], i64 [[IDX]]
+; CHECK-NEXT:    [[RES:%.*]] = call float @llvm.exp.f32(float [[ELEM]])
+; CHECK-NEXT:    [[NEW_VEC:%.*]] = insertelement <vscale x 4 x float> [[VEC]], float [[RES]], i64 [[IDX]]
+; CHECK-NEXT:    [[NEW_IDX]] = add i64 [[IDX]], 1
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i64 [[NEW_IDX]], [[LOOPEND]]
+; CHECK-NEXT:    br i1 [[CMP]], label %[[LOOPEXIT:.*]], label %[[LOOPBODY]]
+; CHECK:       [[LOOPEXIT]]:
+; CHECK-NEXT:    ret <vscale x 4 x float> [[NEW_VEC]]
+  %1 = call <vscale x 4 x float> @llvm.exp.nxv4f32(<vscale x 4 x float> zeroinitializer)
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arsenm wrote:

Also test preservation of flags and metadata 

https://github.com/llvm/llvm-project/pull/117568