[AArch64][GlobalISel] Make G_PTRTOINT only legal for s64 + p0

[paquette]

Summary

A few issues:

1. There was no legalizer test for G_PTRTOINT
2. Same clamping issue as in many other opcodes
3. AArch64 pointers can only be 64b, so in reality we always have to trunc or extend with any size other than p0 anyway.

This seems to actually produce more correct selection for narrow types as well.

[aemerson]

I think the clamping behavior should only allow s64 result types, since AArch64 pointers can only be 64b.

[paquette]

Always clamp to s64

[aemerson]

llvm/test/CodeGen/AArch64/GlobalISel/legalize-ptrtoint.mir

28

I expected these to change?

[paquette]

llvm/test/CodeGen/AArch64/GlobalISel/legalize-ptrtoint.mir

28

The existing legality behaviour says it's okay:

.legalForCartesianProduct({s1, s8, s16, s32, s64}, {p0})

Should we just drop everything except for s64 entirely?

[aemerson]

llvm/test/CodeGen/AArch64/GlobalISel/legalize-ptrtoint.mir

28

Yes I think so.

[paquette]

Only allow s64.

I think that, running through to selection, this actually fixes a couple bugs too. (ptrtoint_s16_p0 and ptrtoint_s8_p0 were using sub_32???)

[aemerson]

LGTM.

llvm/lib/Target/AArch64/GISel/AArch64LegalizerInfo.cpp

AArch64LegalizerInfo::AArch64LegalizerInfo(const AArch64Subtarget &ST)
 
   if (TM.getCodeModel() == CodeModel::Small)
     getActionDefinitionsBuilder(G_GLOBAL_VALUE).custom();
   else
     getActionDefinitionsBuilder(G_GLOBAL_VALUE).legalFor({p0});
 
   getActionDefinitionsBuilder(G_PTRTOINT)
       .legalForCartesianProduct({s1, s8, s16, s32, s64}, {p0})
-      .maxScalar(0, s64)
-      .widenScalarToNextPow2(0, /*Min*/ 8);
+      .widenScalarToNextPow2(0, /*Min*/ 8)
+      .maxScalar(0, s64);
 
   getActionDefinitionsBuilder(G_INTTOPTR)
       .unsupportedIf([&](const LegalityQuery &Query) {
         return Query.Types[0].getSizeInBits() != Query.Types[1].getSizeInBits();
       })
       .legalFor({{p0, s64}, {v2p0, v2s64}});
 
   // Casts for 32 and 64-bit width type are just copies.

llvm/test/CodeGen/AArch64/GlobalISel/legalize-ptrtoint.mir

+# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py
+# RUN: llc -mtriple aarch64 -run-pass=legalizer -verify-machineinstrs -o - %s  | FileCheck %s
+
+...
+---
+name: p0_s64
+body: |
+  bb.0:
+    liveins: $x0
+    ; CHECK-LABEL: name: p0_s64
+    ; CHECK: %ptr:_(p0) = COPY $x0
+    ; CHECK: %int:_(s64) = G_PTRTOINT %ptr(p0)
+    ; CHECK: $x0 = COPY %int(s64)
+    ; CHECK: RET_ReallyLR implicit $x0
+    %ptr:_(p0) = COPY $x0
+    %int:_(s64) = G_PTRTOINT %ptr
+    $x0 = COPY %int
+    RET_ReallyLR implicit $x0
+...
+---
+name: p0_s32
+body: |
+  bb.0:
+    liveins: $x0
+    ; CHECK-LABEL: name: p0_s32
+    ; CHECK: %ptr:_(p0) = COPY $x0
+    ; CHECK: %int:_(s32) = G_PTRTOINT %ptr(p0)
+    ; CHECK: $w0 = COPY %int(s32)
+    ; CHECK: RET_ReallyLR implicit $w0
+    %ptr:_(p0) = COPY $x0
+    %int:_(s32) = G_PTRTOINT %ptr
+    $w0 = COPY %int
+    RET_ReallyLR implicit $w0
+...
+---
+name: p0_s16
+body: |
+  bb.0:
+    liveins: $x0, $h0
+    ; CHECK-LABEL: name: p0_s16
+    ; CHECK: %ptr:_(p0) = COPY $x0
+    ; CHECK: %int:_(s16) = G_PTRTOINT %ptr(p0)
+    ; CHECK: $h0 = COPY %int(s16)
+    ; CHECK: RET_ReallyLR implicit $h0
+    %ptr:_(p0) = COPY $x0
+    %int:_(s16) = G_PTRTOINT %ptr
+    $h0 = COPY %int
+    RET_ReallyLR implicit $h0
+...
+---
+name: p0_s8
+body: |
+  bb.0:
+    liveins: $x0, $b0
+    ; CHECK-LABEL: name: p0_s8
+    ; CHECK: %ptr:_(p0) = COPY $x0
+    ; CHECK: %int:_(s8) = G_PTRTOINT %ptr(p0)
+    ; CHECK: $b0 = COPY %int(s8)
+    ; CHECK: RET_ReallyLR implicit $b0
+    %ptr:_(p0) = COPY $x0
+    %int:_(s8) = G_PTRTOINT %ptr
+    $b0 = COPY %int
+    RET_ReallyLR implicit $b0
+...
+---
+name: p0_s1
+body: |
+  bb.0:
+    liveins: $x0
+    ; CHECK-LABEL: name: p0_s1
+    ; CHECK: %ptr:_(p0) = COPY $x0
+    ; CHECK: %int:_(s1) = G_PTRTOINT %ptr(p0)
+    ; CHECK: %ext:_(s32) = G_ZEXT %int(s1)
+    ; CHECK: $w0 = COPY %ext(s32)
+    ; CHECK: RET_ReallyLR implicit $w0
+    %ptr:_(p0) = COPY $x0
+    %int:_(s1) = G_PTRTOINT %ptr
+    %ext:_(s32) = G_ZEXT %int
+    $w0 = COPY %ext
+    RET_ReallyLR implicit $w0
+...
+---
+name: p0_s128
+body: |
+  bb.0:
+    liveins: $x0, $q0
+    ; CHECK-LABEL: name: p0_s128
+    ; CHECK: %ptr:_(p0) = COPY $x0
+    ; CHECK: [[PTRTOINT:%[0-9]+]]:_(s64) = G_PTRTOINT %ptr(p0)
+    ; CHECK: [[C:%[0-9]+]]:_(s64) = G_CONSTANT i64 0
+    ; CHECK: %int:_(s128) = G_MERGE_VALUES [[PTRTOINT]](s64), [[C]](s64)
+    ; CHECK: $q0 = COPY %int(s128)
+    ; CHECK: RET_ReallyLR implicit $q0
+    %ptr:_(p0) = COPY $x0
+    %int:_(s128) = G_PTRTOINT %ptr
+    $q0 = COPY %int
+    RET_ReallyLR implicit $q0
+...
+---
+name: p0_s88
+body: |
+  bb.0:
+    liveins: $x0
+    ; CHECK-LABEL: name: p0_s88
+    ; CHECK: %ptr:_(p0) = COPY $x0
+    ; CHECK: [[PTRTOINT:%[0-9]+]]:_(s64) = G_PTRTOINT %ptr(p0)
+    ; CHECK: [[C:%[0-9]+]]:_(s64) = G_CONSTANT i64 0
+    ; CHECK: %trunc:_(s32) = G_TRUNC [[PTRTOINT]](s64)
+    ; CHECK: $w0 = COPY %trunc(s32)
+    ; CHECK: RET_ReallyLR implicit $w0
+    %ptr:_(p0) = COPY $x0
+    %int:_(s88) = G_PTRTOINT %ptr
+    %trunc:_(s32) = G_TRUNC %int
+    $w0 = COPY %trunc
+    RET_ReallyLR implicit $w0
+...