[gcc r11-8939] rs6000: Disable mode promotion for pseudos

[gcc r11-8939] rs6000: Disable mode promotion for pseudos

[Segher Boessenkool]

https://gcc.gnu.org/g:5803a97319245cf7942e544a7be7b24821dc7c9e

commit r11-8939-g5803a97319245cf7942e544a7be7b24821dc7c9e
Author: Haochen Gui <guihaoc@gcc.gnu.org>
Date:   Fri Jun 4 14:38:53 2021 +0800

    rs6000: Disable mode promotion for pseudos
    
    rs6000 has instructions that can do almost everything 32 bit
    at least as efficiently as corresponding 64 bit things. The
    mode promotion can be defered to when a wide mode is necessary.
    So it helps a lot not promote mode for pseudos. SPECint test
    shows that the overall performance improvement (by geomean) is
    more than 2% with this patch.
    
    testsuite/gcc.target/powerpc/not-promote-mode.c illustrates how
    the patch eliminates the redundant extensions and do further
    optimization by disabling mode promotion for pseduos.
    
    gcc/ChangeLog
    
            * config/rs6000/rs6000.h (PROMOTE_MODE): Remove.
    
    gcc/testsuite/ChangeLog:
    
            * gcc.target/powerpc/not-promote-mode.c: New.
    
    (cherry picked from commit 9080a3bf23297885fdc47221da37a71d6dec93c5)

Diff:
---
 gcc/config/rs6000/rs6000.h                          | 11 -----------
 gcc/testsuite/gcc.target/powerpc/not-promote-mode.c | 13 +++++++++++++
 2 files changed, 13 insertions(+), 11 deletions(-)

diff --git a/gcc/config/rs6000/rs6000.h b/gcc/config/rs6000/rs6000.h
index a7953fad965..4ca6372435d 100644
--- a/gcc/config/rs6000/rs6000.h
+++ b/gcc/config/rs6000/rs6000.h
@@ -667,17 +667,6 @@ extern unsigned char rs6000_recip_bits[];
 \f
 /* Target machine storage layout.  */
 
-/* Define this macro if it is advisable to hold scalars in registers
-   in a wider mode than that declared by the program.  In such cases,
-   the value is constrained to be within the bounds of the declared
-   type, but kept valid in the wider mode.  The signedness of the
-   extension may differ from that of the type.  */
-
-#define PROMOTE_MODE(MODE,UNSIGNEDP,TYPE)	\
-  if (GET_MODE_CLASS (MODE) == MODE_INT		\
-      && GET_MODE_SIZE (MODE) < (TARGET_32BIT ? 4 : 8)) \
-    (MODE) = TARGET_32BIT ? SImode : DImode;
-
 /* Define this if most significant bit is lowest numbered
    in instructions that operate on numbered bit-fields.  */
 /* That is true on RS/6000.  */
diff --git a/gcc/testsuite/gcc.target/powerpc/not-promote-mode.c b/gcc/testsuite/gcc.target/powerpc/not-promote-mode.c
new file mode 100644
index 00000000000..29af1f8323e
--- /dev/null
+++ b/gcc/testsuite/gcc.target/powerpc/not-promote-mode.c
@@ -0,0 +1,13 @@
+/* { dg-do compile { target { lp64 } } } */
+/* { dg-options "-O2" } */
+
+extern void bar ();
+
+void foo ()
+{
+  int i;
+  for (i = 0; i < 10000; i++)
+    bar ();
+}
+
+/* { dg-final { scan-assembler-not   {\mrldicl\M} } } */