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
+
+// FIXME? Maybe this could be a TableGen attribute on some registers and
+// this table could be generated automatically from RegInfo.
+unsigned MipsTargetLowering::getRegisterByName(const char* RegName,
+ EVT VT) const {
+ // Named registers is expected to be fairly rare. For now, just support $28
+ // since the linux kernel uses it.
+ if (Subtarget.isGP64bit()) {
+ unsigned Reg = StringSwitch<unsigned>(RegName)
+ .Case("$28", Mips::GP_64)
+ .Default(0);
+ if (Reg)
+ return Reg;
+ } else {
+ unsigned Reg = StringSwitch<unsigned>(RegName)
+ .Case("$28", Mips::GP)
+ .Default(0);
+ if (Reg)
+ return Reg;
+ }
+ report_fatal_error("Invalid register name global variable");
+}
void HandleByVal(CCState *, unsigned &, unsigned) const override;
void HandleByVal(CCState *, unsigned &, unsigned) const override;
+ unsigned getRegisterByName(const char* RegName, EVT VT) const override;
+
protected:
SDValue getGlobalReg(SelectionDAG &DAG, EVT Ty) const;
protected:
SDValue getGlobalReg(SelectionDAG &DAG, EVT Ty) const;
--- /dev/null
+; RUN: llc -march=mips64 -relocation-model=static -mattr=+noabicalls,-n64,+n32 < %s | FileCheck %s
+
+define i32* @get_gp() {
+entry:
+ %0 = call i64 @llvm.read_register.i64(metadata !0)
+ %1 = trunc i64 %0 to i32
+ %2 = inttoptr i32 %1 to i32*
+ ret i32* %2
+}
+
+; CHECK-LABEL: get_gp:
+; CHECK: sll $2, $gp, 0
+
+declare i64 @llvm.read_register.i64(metadata)
+
+!llvm.named.register.$28 = !{!0}
+
+!0 = !{!"$28"}
--- /dev/null
+; RUN: llc -march=mips64 -relocation-model=static -mattr=+noabicalls < %s | FileCheck %s
+
+define i32* @get_gp() {
+entry:
+ %0 = call i64 @llvm.read_register.i64(metadata !0)
+ %1 = inttoptr i64 %0 to i32*
+ ret i32* %1
+}
+
+; CHECK-LABEL: get_gp:
+; CHECK: move $2, $gp
+
+declare i64 @llvm.read_register.i64(metadata)
+
+!llvm.named.register.$28 = !{!0}
+
+!0 = !{!"$28"}
--- /dev/null
+; RUN: llc -march=mips -relocation-model=static -mattr=+noabicalls < %s | FileCheck %s
+
+define i32* @get_gp() {
+entry:
+ %0 = call i32 @llvm.read_register.i32(metadata !0)
+ %1 = inttoptr i32 %0 to i32*
+ ret i32* %1
+}
+
+; CHECK-LABEL: get_gp:
+; CHECK: move $2, $gp
+
+declare i32 @llvm.read_register.i32(metadata)
+
+!llvm.named.register.$28 = !{!0}
+
+!0 = !{!"$28"}