[llvm-commits] [llvm] r92511 - /llvm/trunk/lib/Target/X86/README.txt

[Dan Gohman]

Author: djg
Date: Mon Jan  4 14:55:05 2010
New Revision: 92511

URL: http://llvm.org/viewvc/llvm-project?rev=92511&view=rev
Log:
Remove some README.txt entries which are now implemented.

Modified:
    llvm/trunk/lib/Target/X86/README.txt

Modified: llvm/trunk/lib/Target/X86/README.txt
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/README.txt?rev=92511&r1=92510&r2=92511&view=diff

==============================================================================
--- llvm/trunk/lib/Target/X86/README.txt (original)
+++ llvm/trunk/lib/Target/X86/README.txt Mon Jan  4 14:55:05 2010
@@ -530,7 +530,7 @@
 
 //===---------------------------------------------------------------------===//
 
-Start using the flags more.  For example, compile:
+Use the FLAGS values from arithmetic instructions more.  For example, compile:
 
 int add_zf(int *x, int y, int a, int b) {
      if ((*x += y) == 0)
@@ -554,31 +554,8 @@
         movl %ecx, %eax
         ret
 
-and:
-
-int add_zf(int *x, int y, int a, int b) {
-     if ((*x + y) < 0)
-          return a;
-     else
-          return b;
-}
-
-to:
-
-add_zf:
-        addl    (%rdi), %esi
-        movl    %edx, %eax
-        cmovns  %ecx, %eax
-        ret
-
-instead of:
-
-_add_zf:
-        addl (%rdi), %esi
-        testl %esi, %esi
-        cmovs %edx, %ecx
-        movl %ecx, %eax
-        ret
+As another example, compile function f2 in test/CodeGen/X86/cmp-test.ll
+without a test instruction.
 
 //===---------------------------------------------------------------------===//
 
@@ -685,55 +662,6 @@
 
 //===---------------------------------------------------------------------===//
 
-We need to teach the codegen to convert two-address INC instructions to LEA
-when the flags are dead (likewise dec).  For example, on X86-64, compile:
-
-int foo(int A, int B) {
-  return A+1;
-}
-
-to:
-
-_foo:
-        leal    1(%edi), %eax
-        ret
-
-instead of:
-
-_foo:
-        incl %edi
-        movl %edi, %eax
-        ret
-
-Another example is:
-
-;; X's live range extends beyond the shift, so the register allocator
-;; cannot coalesce it with Y.  Because of this, a copy needs to be
-;; emitted before the shift to save the register value before it is
-;; clobbered.  However, this copy is not needed if the register
-;; allocator turns the shift into an LEA.  This also occurs for ADD.
-
-; Check that the shift gets turned into an LEA.
-; RUN: llvm-as < %s | llc -march=x86 -x86-asm-syntax=intel | \
-; RUN:   not grep {mov E.X, E.X}
-
- at G = external global i32		; <i32*> [#uses=3]
-
-define i32 @test1(i32 %X, i32 %Y) {
-	%Z = add i32 %X, %Y		; <i32> [#uses=1]
-	volatile store i32 %Y, i32* @G
-	volatile store i32 %Z, i32* @G
-	ret i32 %X
-}
-
-define i32 @test2(i32 %X) {
-	%Z = add i32 %X, 1		; <i32> [#uses=1]
-	volatile store i32 %Z, i32* @G
-	ret i32 %X
-}
-
-//===---------------------------------------------------------------------===//
-
 Sometimes it is better to codegen subtractions from a constant (e.g. 7-x) with
 a neg instead of a sub instruction.  Consider:
 
@@ -854,11 +782,6 @@
 
 //===---------------------------------------------------------------------===//
 
-Re-materialize MOV32r0 etc. with xor instead of changing them to moves if the
-condition register is dead. xor reg reg is shorter than mov reg, #0.
-
-//===---------------------------------------------------------------------===//
-
 The following code:
 
 bb114.preheader:		; preds = %cond_next94