[llvm] r243576 - AArch64: use 32-bit MOV rather than UBFX to truncate registers.

Tim Northover tnorthover at apple.com
Wed Jul 29 14:34:32 PDT 2015 

Author: tnorthover
Date: Wed Jul 29 16:34:32 2015
New Revision: 243576

URL: http://llvm.org/viewvc/llvm-project?rev=243576&view=rev
Log:
AArch64: use 32-bit MOV rather than UBFX to truncate registers.

It's potentially more efficient on Cyclone, and from the optimization guides &
schedulers looks like it has no effect on Cortex-A53 or A57. In general you'd
expect a MOV to be about the most efficient instruction with its semantics,
even though the official "UXTW" alias is really a UBFX.

Modified:
    llvm/trunk/lib/Target/AArch64/AArch64InstrInfo.td
    llvm/trunk/test/CodeGen/AArch64/aarch64-dynamic-stack-layout.ll
    llvm/trunk/test/CodeGen/AArch64/arm64-aapcs.ll
    llvm/trunk/test/CodeGen/AArch64/arm64-popcnt.ll
    llvm/trunk/test/CodeGen/AArch64/bitfield.ll

Modified: llvm/trunk/lib/Target/AArch64/AArch64InstrInfo.td
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/AArch64/AArch64InstrInfo.td?rev=243576&r1=243575&r2=243576&view=diff
==============================================================================
--- llvm/trunk/lib/Target/AArch64/AArch64InstrInfo.td (original)
+++ llvm/trunk/lib/Target/AArch64/AArch64InstrInfo.td Wed Jul 29 16:34:32 2015
@@ -5148,10 +5148,10 @@ def : Pat<(i64 (zext def32:$src)), (SUBR
 def : Pat<(i64 (anyext GPR32:$src)),
           (INSERT_SUBREG (i64 (IMPLICIT_DEF)), GPR32:$src, sub_32)>;
 
-// When we need to explicitly zero-extend, we use an unsigned bitfield move
-// instruction (UBFM) on the enclosing super-reg.
+// When we need to explicitly zero-extend, we use a 32-bit MOV instruction and
+// then assert the extension has happened.
 def : Pat<(i64 (zext GPR32:$src)),
- (UBFMXri (INSERT_SUBREG (i64 (IMPLICIT_DEF)), GPR32:$src, sub_32), 0, 31)>;
+          (SUBREG_TO_REG (i32 0), (ORRWrs WZR, GPR32:$src, 0), sub_32)>;
 
 // To sign extend, we use a signed bitfield move instruction (SBFM) on the
 // containing super-reg.

Modified: llvm/trunk/test/CodeGen/AArch64/aarch64-dynamic-stack-layout.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/AArch64/aarch64-dynamic-stack-layout.ll?rev=243576&r1=243575&r2=243576&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/AArch64/aarch64-dynamic-stack-layout.ll (original)
+++ llvm/trunk/test/CodeGen/AArch64/aarch64-dynamic-stack-layout.ll Wed Jul 29 16:34:32 2015
@@ -252,11 +252,11 @@ entry:
 ; CHECK: ldr	w[[IARG:[0-9]+]], [x29, #24]
 ; CHECK: ldr	d[[DARG:[0-9]+]], [x29, #40]
 ;   Check correct reservation of 16-byte aligned VLA (size in w0) on stack
-; CHECK: ubfx	x9, x0, #0, #32
+; CHECK: mov	w9, w0
+; CHECK: mov	 x10, sp
 ; CHECK: lsl	x9, x9, #2
 ; CHECK: add	x9, x9, #15
 ; CHECK: and	x9, x9, #0x7fffffff0
-; CHECK: mov	 x10, sp
 ; CHECK: sub	 x[[VLASPTMP:[0-9]+]], x10, x9
 ; CHECK: mov	 sp, x[[VLASPTMP]]
 ;   Check correct access to local variable, through frame pointer
@@ -299,11 +299,11 @@ entry:
 ; CHECK: ldr	w[[IARG:[0-9]+]], [x29, #24]
 ; CHECK: ldr	d[[DARG:[0-9]+]], [x29, #40]
 ;   Check correct reservation of 16-byte aligned VLA (size in w0) on stack
-; CHECK: ubfx	x9, x0, #0, #32
+; CHECK: mov	w9, w0
+; CHECK: mov	 x10, sp
 ; CHECK: lsl	x9, x9, #2
 ; CHECK: add	x9, x9, #15
 ; CHECK: and	x9, x9, #0x7fffffff0
-; CHECK: mov	 x10, sp
 ; CHECK: sub	 x[[VLASPTMP:[0-9]+]], x10, x9
 ; CHECK: mov	 sp, x[[VLASPTMP]]
 ;   Check correct access to local variable, through frame pointer
@@ -361,11 +361,11 @@ entry:
 ; CHECK: ldr	d[[DARG:[0-9]+]], [x29, #40]
 ;   Check correct reservation of 16-byte aligned VLA (size in w0) on stack
 ;   and set-up of base pointer (x19).
-; CHECK: ubfx	x9, x0, #0, #32
+; CHECK: mov	w9, w0
+; CHECK: mov	 x10, sp
 ; CHECK: lsl	x9, x9, #2
 ; CHECK: add	x9, x9, #15
 ; CHECK: and	x9, x9, #0x7fffffff0
-; CHECK: mov	 x10, sp
 ; CHECK: sub	 x[[VLASPTMP:[0-9]+]], x10, x9
 ; CHECK: mov	 sp, x[[VLASPTMP]]
 ;   Check correct access to local variable, through base pointer
@@ -414,11 +414,11 @@ entry:
 ; CHECK: ldr	d[[DARG:[0-9]+]], [x29, #40]
 ;   Check correct reservation of 16-byte aligned VLA (size in w0) on stack
 ;   and set-up of base pointer (x19).
-; CHECK: ubfx	x9, x0, #0, #32
+; CHECK: mov	w9, w0
+; CHECK: mov	 x10, sp
 ; CHECK: lsl	x9, x9, #2
 ; CHECK: add	x9, x9, #15
 ; CHECK: and	x9, x9, #0x7fffffff0
-; CHECK: mov	 x10, sp
 ; CHECK: sub	 x[[VLASPTMP:[0-9]+]], x10, x9
 ; CHECK: mov	 sp, x[[VLASPTMP]]
 ;   Check correct access to local variable, through base pointer
@@ -465,11 +465,11 @@ entry:
 ; CHECK: ldr	d[[DARG:[0-9]+]], [x29, #40]
 ;   Check correct reservation of 16-byte aligned VLA (size in w0) on stack
 ;   and set-up of base pointer (x19).
-; CHECK: ubfx	x9, x0, #0, #32
+; CHECK: mov	w9, w0
+; CHECK: mov	 x10, sp
 ; CHECK: lsl	x9, x9, #2
 ; CHECK: add	x9, x9, #15
 ; CHECK: and	x9, x9, #0x7fffffff0
-; CHECK: mov	 x10, sp
 ; CHECK: sub	 x[[VLASPTMP:[0-9]+]], x10, x9
 ; CHECK: mov	 sp, x[[VLASPTMP]]
 ;   Check correct access to local variable, through base pointer

Modified: llvm/trunk/test/CodeGen/AArch64/arm64-aapcs.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/AArch64/arm64-aapcs.ll?rev=243576&r1=243575&r2=243576&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/AArch64/arm64-aapcs.ll (original)
+++ llvm/trunk/test/CodeGen/AArch64/arm64-aapcs.ll Wed Jul 29 16:34:32 2015
@@ -78,8 +78,8 @@ define void @test_extension(i1 %bool, i8
 
   %ext_int = zext i32 %int to i64
   store volatile i64 %ext_int, i64* @var64
-; CHECK: ubfx [[EXT:x[0-9]+]], x3, #0, #32
-; CHECK: str [[EXT]], [{{x[0-9]+}}, :lo12:var64]
+; CHECK: mov w[[EXT:[0-9]+]], w3
+; CHECK: str x[[EXT]], [{{x[0-9]+}}, :lo12:var64]
 
   ret void
 }

Modified: llvm/trunk/test/CodeGen/AArch64/arm64-popcnt.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/AArch64/arm64-popcnt.ll?rev=243576&r1=243575&r2=243576&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/AArch64/arm64-popcnt.ll (original)
+++ llvm/trunk/test/CodeGen/AArch64/arm64-popcnt.ll Wed Jul 29 16:34:32 2015
@@ -4,8 +4,8 @@
 define i32 @cnt32_advsimd(i32 %x) nounwind readnone {
   %cnt = tail call i32 @llvm.ctpop.i32(i32 %x)
   ret i32 %cnt
-; CHECK: ubfx	x{{[0-9]+}}
-; CHECK: fmov	d0, x{{[0-9]+}}
+; CHECK: mov w[[IN64:[0-9]+]], w0
+; CHECK: fmov	d0, x[[IN64]]
 ; CHECK: cnt.8b	v0, v0
 ; CHECK: uaddlv.8b	h0, v0
 ; CHECK: fmov w0, s0

Modified: llvm/trunk/test/CodeGen/AArch64/bitfield.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/AArch64/bitfield.ll?rev=243576&r1=243575&r2=243576&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/AArch64/bitfield.ll (original)
+++ llvm/trunk/test/CodeGen/AArch64/bitfield.ll Wed Jul 29 16:34:32 2015
@@ -60,7 +60,7 @@ define void @test_extendw(i32 %var) {
 
   %uxt64 = zext i32 %var to i64
   store volatile i64 %uxt64, i64* @var64
-; CHECK: ubfx {{x[0-9]+}}, {{x[0-9]+}}, #0, #32
+; CHECK: mov {{w[0-9]+}}, w0
   ret void
 }

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