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[FastISel][AArch64] Fold offset into the memory operation. 

Fold simple offsets into the memory operation:
  add x0, x0, #8
  ldr x0, [x0]
-->
  ldr x0, [x0, #8]

Fixes <rdar://problem/17887945>.

llvm-svn: 214545
This commit is contained in:
Juergen Ributzka 2014-08-01 19:40:16 +00:00
parent f164bee0e0
commit 5dcb33bdbb
2 changed files with 30 additions and 0 deletions
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7
llvm/lib/Target/AArch64/AArch64FastISel.cpp
View File

@ -419,6 +419,13 @@ bool AArch64FastISel::ComputeAddress(const Value *Obj, Address &Addr) {
}
break;
}
case Instruction::Add:
// Adds of constants are common and easy enough.
if (const ConstantInt *CI = dyn_cast<ConstantInt>(U->getOperand(1))) {
Addr.setOffset(Addr.getOffset() + (uint64_t)CI->getSExtValue());
return ComputeAddress(U->getOperand(0), Addr);
}
break;
}
// Try to get this in a register if nothing else has worked.

23
llvm/test/CodeGen/AArch64/fast-isel-compute-address.ll Normal file
View File

@ -0,0 +1,23 @@
; RUN: llc -fast-isel -fast-isel-abort -mtriple=arm64-apple-darwin < %s | FileCheck %s
; Test simple constant offset.
define i64 @test_load1(i64 %a) {
; CHECK-LABEL: test_load1
; CHECK: ldr x0, [x0, #16]
%1 = add i64 %a, 16
%2 = inttoptr i64 %1 to i64*
%3 = load i64* %2
ret i64 %3
}
; Test large constant offset.
define i64 @test_load2(i64 %a) {
; CHECK-LABEL: test_load2
; CHECK: add [[REG:x[0-9]+]], x0, {{x[0-9]+}}
; CHECK: ldr x0, {{\[}}[[REG]]{{\]}}
%1 = add i64 %a, 16777216
%2 = inttoptr i64 %1 to i64*
%3 = load i64* %2
ret i64 %3
}