[llvm] [GISel][RISCV][AArch64] Support legalizing G_SCMP/G_UCMP to sub(isgt,islt). (PR #119265)

[Craig Topper via llvm-commits]

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@@ -61,42 +61,13 @@ body:             |
     ; CHECK-NEXT: [[COPY6:%[0-9]+]]:_(s32) = COPY $w2
     ; CHECK-NEXT: [[COPY7:%[0-9]+]]:_(s32) = COPY $w3
     ; CHECK-NEXT: [[BUILD_VECTOR1:%[0-9]+]]:_(<4 x s32>) = G_BUILD_VECTOR [[COPY]](s32), [[COPY1]](s32), [[COPY2]](s32), [[COPY3]](s32)
-    ; CHECK-NEXT: [[C:%[0-9]+]]:_(s8) = G_CONSTANT i8 1
-    ; CHECK-NEXT: [[C1:%[0-9]+]]:_(s8) = G_CONSTANT i8 0
     ; CHECK-NEXT: [[ICMP:%[0-9]+]]:_(<4 x s32>) = G_ICMP intpred(ugt), [[BUILD_VECTOR]](<4 x s32>), [[BUILD_VECTOR1]]
-    ; CHECK-NEXT: [[C2:%[0-9]+]]:_(s8) = G_CONSTANT i8 3
-    ; CHECK-NEXT: [[TRUNC:%[0-9]+]]:_(<4 x s16>) = G_TRUNC [[ICMP]](<4 x s32>)
-    ; CHECK-NEXT: [[DEF:%[0-9]+]]:_(s8) = G_IMPLICIT_DEF
-    ; CHECK-NEXT: [[BUILD_VECTOR2:%[0-9]+]]:_(<8 x s8>) = G_BUILD_VECTOR [[C2]](s8), [[C2]](s8), [[C2]](s8), [[C2]](s8), [[DEF]](s8), [[DEF]](s8), [[DEF]](s8), [[DEF]](s8)
-    ; CHECK-NEXT: [[ANYEXT:%[0-9]+]]:_(<8 x s16>) = G_ANYEXT [[BUILD_VECTOR2]](<8 x s8>)
-    ; CHECK-NEXT: [[UV:%[0-9]+]]:_(<4 x s16>), [[UV1:%[0-9]+]]:_(<4 x s16>) = G_UNMERGE_VALUES [[ANYEXT]](<8 x s16>)
-    ; CHECK-NEXT: [[XOR:%[0-9]+]]:_(<4 x s16>) = G_XOR [[TRUNC]], [[UV]]
-    ; CHECK-NEXT: [[BUILD_VECTOR3:%[0-9]+]]:_(<8 x s8>) = G_BUILD_VECTOR [[C]](s8), [[C]](s8), [[C]](s8), [[C]](s8), [[DEF]](s8), [[DEF]](s8), [[DEF]](s8), [[DEF]](s8)
-    ; CHECK-NEXT: [[ANYEXT1:%[0-9]+]]:_(<8 x s16>) = G_ANYEXT [[BUILD_VECTOR3]](<8 x s8>)
-    ; CHECK-NEXT: [[UV2:%[0-9]+]]:_(<4 x s16>), [[UV3:%[0-9]+]]:_(<4 x s16>) = G_UNMERGE_VALUES [[ANYEXT1]](<8 x s16>)
-    ; CHECK-NEXT: [[TRUNC1:%[0-9]+]]:_(<4 x s16>) = G_TRUNC [[ICMP]](<4 x s32>)
-    ; CHECK-NEXT: [[AND:%[0-9]+]]:_(<4 x s16>) = G_AND [[UV2]], [[TRUNC1]]
-    ; CHECK-NEXT: [[BUILD_VECTOR4:%[0-9]+]]:_(<8 x s8>) = G_BUILD_VECTOR [[C1]](s8), [[C1]](s8), [[C1]](s8), [[C1]](s8), [[DEF]](s8), [[DEF]](s8), [[DEF]](s8), [[DEF]](s8)
-    ; CHECK-NEXT: [[ANYEXT2:%[0-9]+]]:_(<8 x s16>) = G_ANYEXT [[BUILD_VECTOR4]](<8 x s8>)
-    ; CHECK-NEXT: [[UV4:%[0-9]+]]:_(<4 x s16>), [[UV5:%[0-9]+]]:_(<4 x s16>) = G_UNMERGE_VALUES [[ANYEXT2]](<8 x s16>)
-    ; CHECK-NEXT: [[AND1:%[0-9]+]]:_(<4 x s16>) = G_AND [[UV4]], [[XOR]]
-    ; CHECK-NEXT: [[OR:%[0-9]+]]:_(<4 x s16>) = G_OR [[AND]], [[AND1]]
-    ; CHECK-NEXT: [[C3:%[0-9]+]]:_(s8) = G_CONSTANT i8 3
     ; CHECK-NEXT: [[ICMP1:%[0-9]+]]:_(<4 x s32>) = G_ICMP intpred(ult), [[BUILD_VECTOR]](<4 x s32>), [[BUILD_VECTOR1]]
-    ; CHECK-NEXT: [[TRUNC2:%[0-9]+]]:_(<4 x s16>) = G_TRUNC [[ICMP1]](<4 x s32>)
-    ; CHECK-NEXT: [[BUILD_VECTOR5:%[0-9]+]]:_(<8 x s8>) = G_BUILD_VECTOR [[C3]](s8), [[C3]](s8), [[C3]](s8), [[C3]](s8), [[DEF]](s8), [[DEF]](s8), [[DEF]](s8), [[DEF]](s8)
-    ; CHECK-NEXT: [[ANYEXT3:%[0-9]+]]:_(<8 x s16>) = G_ANYEXT [[BUILD_VECTOR5]](<8 x s8>)
-    ; CHECK-NEXT: [[UV6:%[0-9]+]]:_(<4 x s16>), [[UV7:%[0-9]+]]:_(<4 x s16>) = G_UNMERGE_VALUES [[ANYEXT3]](<8 x s16>)
-    ; CHECK-NEXT: [[XOR1:%[0-9]+]]:_(<4 x s16>) = G_XOR [[TRUNC2]], [[UV6]]
-    ; CHECK-NEXT: [[BUILD_VECTOR6:%[0-9]+]]:_(<8 x s8>) = G_BUILD_VECTOR [[C3]](s8), [[C3]](s8), [[C3]](s8), [[C3]](s8), [[DEF]](s8), [[DEF]](s8), [[DEF]](s8), [[DEF]](s8)
-    ; CHECK-NEXT: [[ANYEXT4:%[0-9]+]]:_(<8 x s16>) = G_ANYEXT [[BUILD_VECTOR6]](<8 x s8>)
-    ; CHECK-NEXT: [[UV8:%[0-9]+]]:_(<4 x s16>), [[UV9:%[0-9]+]]:_(<4 x s16>) = G_UNMERGE_VALUES [[ANYEXT4]](<8 x s16>)
-    ; CHECK-NEXT: [[TRUNC3:%[0-9]+]]:_(<4 x s16>) = G_TRUNC [[ICMP1]](<4 x s32>)
-    ; CHECK-NEXT: [[AND2:%[0-9]+]]:_(<4 x s16>) = G_AND [[UV8]], [[TRUNC3]]
-    ; CHECK-NEXT: [[AND3:%[0-9]+]]:_(<4 x s16>) = G_AND [[OR]], [[XOR1]]
-    ; CHECK-NEXT: [[OR1:%[0-9]+]]:_(<4 x s16>) = G_OR [[AND2]], [[AND3]]
-    ; CHECK-NEXT: [[ANYEXT5:%[0-9]+]]:_(<4 x s32>) = G_ANYEXT [[OR1]](<4 x s16>)
-    ; CHECK-NEXT: [[SEXT_INREG:%[0-9]+]]:_(<4 x s32>) = G_SEXT_INREG [[ANYEXT5]], 2
+    ; CHECK-NEXT: [[TRUNC:%[0-9]+]]:_(<4 x s16>) = G_TRUNC [[ICMP1]](<4 x s32>)
----------------
topperc wrote:

This isn't optimal because the G_ICMP we create with <4 x i1> is legalized to <4 x i32>. The G_SUB we created had <4 x i2> type. It was legalized to <4 x i16>. So a trunc was required. This could probably be fixed by widening the G_UCMP result type to match the input type before lowering.

https://github.com/llvm/llvm-project/pull/119265