[PATCH] D154979: [RISCV] Add test for vmerge combine that should be prevented

[Luke Lau via Phabricator via llvm-commits]

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The fadd in these test cases is constrained and may set fflags differently
depending on the active elements (the nofpexcept flag isn't set on the node).
Therefore to preserve semantics we shouldn't change its mask.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D154979

Files:
  llvm/test/CodeGen/RISCV/rvv/rvv-peephole-vmerge-vops.ll


Index: llvm/test/CodeGen/RISCV/rvv/rvv-peephole-vmerge-vops.ll
===================================================================
--- llvm/test/CodeGen/RISCV/rvv/rvv-peephole-vmerge-vops.ll
+++ llvm/test/CodeGen/RISCV/rvv/rvv-peephole-vmerge-vops.ll
@@ -361,6 +361,37 @@
   ret <vscale x 2 x float> %b
 }
 
+; This shouldn't be folded because the vfadd may raise exceptions, and changing
+; the mask on the vfadd might prevent it from being raised
+define <vscale x 2 x float> @vpmerge_constrained_fadd(<vscale x 2 x float> %passthru, <vscale x 2 x float> %x, <vscale x 2 x float> %y, <vscale x 2 x i1> %m, i64 %vl) strictfp {
+; CHECK-LABEL: vpmerge_constrained_fadd:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    vsetvli a1, zero, e32, m1, ta, ma
+; CHECK-NEXT:    vfadd.vv v9, v9, v10
+; CHECK-NEXT:    vsetvli zero, a0, e32, m1, tu, ma
+; CHECK-NEXT:    vmerge.vvm v8, v8, v9, v0
+; CHECK-NEXT:    ret
+  ; %a = fadd <vscale x 2 x float> %x, %y
+  %a = call <vscale x 2 x float> @llvm.experimental.constrained.fadd(<vscale x 2 x float> %x, <vscale x 2 x float> %y, metadata !"round.dynamic", metadata !"fpexcept.strict") strictfp
+  %b = call <vscale x 2 x float> @llvm.riscv.vmerge.nxv2f32.nxv2f32(<vscale x 2 x float> %passthru, <vscale x 2 x float> %passthru, <vscale x 2 x float> %a, <vscale x 2 x i1> %m, i64 %vl)
+  ret <vscale x 2 x float> %b
+}
+declare <vscale x 2 x float> @llvm.experimental.constrained.fadd(<vscale x 2 x float>, <vscale x 2 x float>, metadata, metadata)
+declare <vscale x 2 x float> @llvm.riscv.vmerge.nxv2f32.nxv2f32(<vscale x 2 x float>, <vscale x 2 x float>, <vscale x 2 x float>, <vscale x 2 x i1>, i64)
+
+; FIXME: This shouldn't be folded because the mask has been changed here
+define <vscale x 2 x float> @vpmerge_constrained_fadd_vlmax(<vscale x 2 x float> %passthru, <vscale x 2 x float> %x, <vscale x 2 x float> %y, <vscale x 2 x i1> %m) strictfp {
+; CHECK-LABEL: vpmerge_constrained_fadd_vlmax:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    vsetvli a0, zero, e32, m1, tu, mu
+; CHECK-NEXT:    vfadd.vv v8, v9, v10, v0.t
+; CHECK-NEXT:    ret
+  ; %a = fadd <vscale x 2 x float> %x, %y
+  %a = call <vscale x 2 x float> @llvm.experimental.constrained.fadd(<vscale x 2 x float> %x, <vscale x 2 x float> %y, metadata !"round.dynamic", metadata !"fpexcept.strict") strictfp
+  %b = call <vscale x 2 x float> @llvm.riscv.vmerge.nxv2f32.nxv2f32(<vscale x 2 x float> %passthru, <vscale x 2 x float> %passthru, <vscale x 2 x float> %a, <vscale x 2 x i1> %m, i64 -1)
+  ret <vscale x 2 x float> %b
+}
+
 ; Test conversion by fptosi.
 define <vscale x 2 x i16> @vpmerge_fptosi(<vscale x 2 x i16> %passthru, <vscale x 2 x float> %x, <vscale x 2 x i1> %m, i32 zeroext %vl) {
 ; CHECK-LABEL: vpmerge_fptosi:


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