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[mips] Add support for accessing $gp as a named register.
Summary: Mips Linux uses $gp to hold a pointer to thread info structure and accesses it with a named register. This makes this work for LLVM. The N32 ABI doesn't quite work yet since the frontend generates incorrect IR for this case. It neglects to truncate the 64-bit GPR to a 32-bit value before converting to a pointer. Given correct IR (as in the testcase in this patch), it works correctly. Reviewers: sstankovic, vmedic, atanasyan Reviewed By: atanasyan Subscribers: llvm-commits Differential Revision: http://reviews.llvm.org/D6893 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@225529 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -3839,3 +3839,25 @@ MipsTargetLowering::emitPseudoSELECT(MachineInstr *MI, MachineBasicBlock *BB,
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return BB;
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}
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// FIXME? Maybe this could be a TableGen attribute on some registers and
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// this table could be generated automatically from RegInfo.
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unsigned MipsTargetLowering::getRegisterByName(const char* RegName,
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EVT VT) const {
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// Named registers is expected to be fairly rare. For now, just support $28
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// since the linux kernel uses it.
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if (Subtarget.isGP64bit()) {
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unsigned Reg = StringSwitch<unsigned>(RegName)
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.Case("$28", Mips::GP_64)
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.Default(0);
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if (Reg)
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return Reg;
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} else {
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unsigned Reg = StringSwitch<unsigned>(RegName)
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.Case("$28", Mips::GP)
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.Default(0);
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if (Reg)
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return Reg;
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}
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report_fatal_error("Invalid register name global variable");
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}
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@ -262,6 +262,8 @@ namespace llvm {
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void HandleByVal(CCState *, unsigned &, unsigned) const override;
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unsigned getRegisterByName(const char* RegName, EVT VT) const override;
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protected:
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SDValue getGlobalReg(SelectionDAG &DAG, EVT Ty) const;
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18
test/CodeGen/Mips/named-register-n32.ll
Normal file
18
test/CodeGen/Mips/named-register-n32.ll
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@ -0,0 +1,18 @@
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; RUN: llc -march=mips64 -relocation-model=static -mattr=+noabicalls,-n64,+n32 < %s | FileCheck %s
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define i32* @get_gp() {
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entry:
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%0 = call i64 @llvm.read_register.i64(metadata !0)
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%1 = trunc i64 %0 to i32
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%2 = inttoptr i32 %1 to i32*
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ret i32* %2
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}
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; CHECK-LABEL: get_gp:
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; CHECK: sll $2, $gp, 0
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declare i64 @llvm.read_register.i64(metadata)
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!llvm.named.register.$28 = !{!0}
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!0 = !{!"$28"}
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17
test/CodeGen/Mips/named-register-n64.ll
Normal file
17
test/CodeGen/Mips/named-register-n64.ll
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@ -0,0 +1,17 @@
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; RUN: llc -march=mips64 -relocation-model=static -mattr=+noabicalls < %s | FileCheck %s
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define i32* @get_gp() {
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entry:
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%0 = call i64 @llvm.read_register.i64(metadata !0)
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%1 = inttoptr i64 %0 to i32*
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ret i32* %1
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}
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; CHECK-LABEL: get_gp:
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; CHECK: move $2, $gp
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declare i64 @llvm.read_register.i64(metadata)
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!llvm.named.register.$28 = !{!0}
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!0 = !{!"$28"}
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17
test/CodeGen/Mips/named-register-o32.ll
Normal file
17
test/CodeGen/Mips/named-register-o32.ll
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@ -0,0 +1,17 @@
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; RUN: llc -march=mips -relocation-model=static -mattr=+noabicalls < %s | FileCheck %s
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define i32* @get_gp() {
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entry:
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%0 = call i32 @llvm.read_register.i32(metadata !0)
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%1 = inttoptr i32 %0 to i32*
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ret i32* %1
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}
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; CHECK-LABEL: get_gp:
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; CHECK: move $2, $gp
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declare i32 @llvm.read_register.i32(metadata)
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!llvm.named.register.$28 = !{!0}
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!0 = !{!"$28"}
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