[PATCH] D54174: [GlobalISel] LegalizationArtifactCombiner: Combine aext([asz]ext x) -> [asz]ext x

[Volkan Keles via Phabricator via llvm-commits]

volkan created this revision.
volkan added reviewers: aditya_nandakumar, dsanders, aemerson, bogner.
Herald added subscribers: javed.absar, kristof.beyls, rovka.

Replace `aext([asz]ext x)` with `aext/sext/zext x` in order to
reduce the number of instructions generated to clean up some
legalization artifacts.


https://reviews.llvm.org/D54174

Files:
  include/llvm/CodeGen/GlobalISel/LegalizationArtifactCombiner.h
  test/CodeGen/AArch64/GlobalISel/legalize-ext.mir


Index: test/CodeGen/AArch64/GlobalISel/legalize-ext.mir
===================================================================
--- test/CodeGen/AArch64/GlobalISel/legalize-ext.mir
+++ test/CodeGen/AArch64/GlobalISel/legalize-ext.mir
@@ -51,10 +51,8 @@
     ; CHECK: $w0 = COPY [[ASHR2]](s32)
     ; CHECK: [[C6:%[0-9]+]]:_(s32) = G_CONSTANT i32 1
     ; CHECK: [[TRUNC10:%[0-9]+]]:_(s32) = G_TRUNC [[COPY]](s64)
-    ; CHECK: [[COPY5:%[0-9]+]]:_(s32) = COPY [[C6]](s32)
-    ; CHECK: [[AND3:%[0-9]+]]:_(s32) = G_AND [[TRUNC10]], [[COPY5]]
-    ; CHECK: [[COPY6:%[0-9]+]]:_(s32) = COPY [[AND3]](s32)
-    ; CHECK: $w0 = COPY [[COPY6]](s32)
+    ; CHECK: [[AND3:%[0-9]+]]:_(s32) = G_AND [[TRUNC10]], [[C6]]
+    ; CHECK: $w0 = COPY [[AND3]](s32)
     ; CHECK: [[TRUNC11:%[0-9]+]]:_(s32) = G_TRUNC [[COPY]](s64)
     ; CHECK: $w0 = COPY [[TRUNC11]](s32)
     ; CHECK: [[TRUNC12:%[0-9]+]]:_(s32) = G_TRUNC [[COPY]](s64)
@@ -118,3 +116,59 @@
     $w0 = COPY %27(s32)
 
 ...
+---
+name:            test_anyext_anyext
+body:             |
+  bb.0:
+    liveins: $w0
+
+    ; CHECK-LABEL: name: test_anyext_anyext
+    ; CHECK: [[COPY:%[0-9]+]]:_(s32) = COPY $w0
+    ; CHECK: [[COPY1:%[0-9]+]]:_(s32) = COPY [[COPY]](s32)
+    ; CHECK: $w0 = COPY [[COPY1]](s32)
+    %0:_(s32) = COPY $w0
+    %1:_(s1) = G_TRUNC %0(s32)
+    %2:_(s8) = G_ANYEXT %1(s1)
+    %3:_(s32) = G_ANYEXT %2(s8)
+    $w0 = COPY %3(s32)
+
+...
+---
+name:            test_anyext_sext
+body:             |
+  bb.0:
+    liveins: $w0
+
+    ; CHECK-LABEL: name: test_anyext_sext
+    ; CHECK: [[COPY:%[0-9]+]]:_(s32) = COPY $w0
+    ; CHECK: [[C:%[0-9]+]]:_(s32) = G_CONSTANT i32 31
+    ; CHECK: [[COPY1:%[0-9]+]]:_(s32) = COPY [[COPY]](s32)
+    ; CHECK: [[SHL:%[0-9]+]]:_(s32) = G_SHL [[COPY1]], [[C]]
+    ; CHECK: [[ASHR:%[0-9]+]]:_(s32) = G_ASHR [[SHL]], [[C]]
+    ; CHECK: $w0 = COPY [[ASHR]](s32)
+    %0:_(s32) = COPY $w0
+    %1:_(s1) = G_TRUNC %0(s32)
+    %2:_(s8) = G_SEXT %1(s1)
+    %3:_(s32) = G_ANYEXT %2(s8)
+    $w0 = COPY %3(s32)
+
+...
+---
+name:            test_anyext_zext
+body:             |
+  bb.0:
+    liveins: $w0
+
+    ; CHECK-LABEL: name: test_anyext_zext
+    ; CHECK: [[COPY:%[0-9]+]]:_(s32) = COPY $w0
+    ; CHECK: [[C:%[0-9]+]]:_(s32) = G_CONSTANT i32 1
+    ; CHECK: [[COPY1:%[0-9]+]]:_(s32) = COPY [[COPY]](s32)
+    ; CHECK: [[AND:%[0-9]+]]:_(s32) = G_AND [[COPY1]], [[C]]
+    ; CHECK: $w0 = COPY [[AND]](s32)
+    %0:_(s32) = COPY $w0
+    %1:_(s1) = G_TRUNC %0(s32)
+    %2:_(s8) = G_ZEXT %1(s1)
+    %3:_(s32) = G_ANYEXT %2(s8)
+    $w0 = COPY %3(s32)
+
+...
Index: include/llvm/CodeGen/GlobalISel/LegalizationArtifactCombiner.h
===================================================================
--- include/llvm/CodeGen/GlobalISel/LegalizationArtifactCombiner.h
+++ include/llvm/CodeGen/GlobalISel/LegalizationArtifactCombiner.h
@@ -51,6 +51,18 @@
       markInstAndDefDead(MI, *MRI.getVRegDef(SrcReg), DeadInsts);
       return true;
     }
+
+    // aext([asz]ext x) -> [asz]ext x
+    unsigned ExtSrc;
+    MachineInstr *ExtMI;
+    if (mi_match(SrcReg, MRI,
+                 m_all_of(m_MInstr(ExtMI), m_any_of(m_GAnyExt(m_Reg(ExtSrc)),
+                                                    m_GSExt(m_Reg(ExtSrc)),
+                                                    m_GZExt(m_Reg(ExtSrc)))))) {
+      Builder.buildInstr(ExtMI->getOpcode(), DstReg, ExtSrc);
+      markInstAndDefDead(MI, *ExtMI, DeadInsts);
+      return true;
+    }
     return tryFoldImplicitDef(MI, DeadInsts);
   }
 


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