Suggested -fpregs instead of +soft-float.

Has the same effect, but turning off a feature matches the other flags better than turning on a feature (which actually turns off a feature).

Author: thejpster

src/doc/rustc/src/platform-support/thumbv7em-none-eabi.md

@@ -35,9 +35,9 @@ to use these flags.
 | CPU | FPU | DSP | Target CPU | Target Features |
 | ---------- | --- | --- | ----------- | --------------- |
 | Any | No | Yes | None | None |
-| Cortex-M4 | No | Yes |`cortex-m4`|`+soft-float`|
+| Cortex-M4 | No | Yes |`cortex-m4`|`-fpregs`|
 | Cortex-M4F | SP | Yes |`cortex-m4`| None |
-| Cortex-M7 | No | Yes |`cortex-m7`|`+soft-float`|
+| Cortex-M7 | No | Yes |`cortex-m7`|`-fpregs`|
 | Cortex-M7F | SP | Yes |`cortex-m7`|`-fp64`|
 | Cortex-M7F | DP | Yes |`cortex-m7`| None |
 
@@ -50,6 +50,13 @@ to use these flags.
 | Cortex-M7F | SP | Yes |`cortex-m7`|`-fp64`|
 | Cortex-M7F | DP | Yes |`cortex-m7`| None |
 
+<divclass="warning">
+
+Never use the `-fpregs`*target-feature* with these `eabihf` targets
+as it will cause compilation units to have different ABIs, which is unsound.
+
+</div>
+
 ### Arm Cortex-M4 and Arm Cortex-M4F
 
 The target CPU is `cortex-m4`.
@@ -59,7 +66,7 @@ The target CPU is `cortex-m4`.
 * enabled by default with this *target*
 * Cortex-M4F has a single precision FPU
 * support is enabled by default with this *target-cpu*
-* disable support using the `+soft-float`feature (`eabi` only)
+* disable support using the `-fpregs`*target-feature* (`eabi` only)
 
 ### Arm Cortex-M7 and Arm Cortex-M7F
 
@@ -71,4 +78,4 @@ The target CPU is `cortex-m7`.
 * Cortex-M7F have either a single-precision or double-precision FPU
 * double-precision support is enabled by default with this *target-cpu*
 * opt-out by using the `-f64`*target-feature*
-* disable support entirely using the `+soft-float`feature (`eabi` only)
+* disable support entirely using the `-fpregs`*target-feature* (`eabi` only)

src/doc/rustc/src/platform-support/thumbv8m.main-none-eabi.md

@@ -39,22 +39,22 @@ to use these flags.
 | CPU | FPU | DSP | MVE | Target CPU | Target Features |
 | ----------- | --- | --- | --------- | ------------- | --------------------- |
 | Unspecified | No | No | No | None | None |
-| Cortex-M33 | No | No | No |`cortex-m33`|`+soft-float,-dsp`|
-| Cortex-M33 | No | Yes | No |`cortex-m33`|`+soft-float`|
+| Cortex-M33 | No | No | No |`cortex-m33`|`-fpregs,-dsp`|
+| Cortex-M33 | No | Yes | No |`cortex-m33`|`-fpregs`|
 | Cortex-M33 | SP | No | No |`cortex-m33`|`-dsp`|
 | Cortex-M33 | SP | Yes | No |`cortex-m33`| None |
-| Cortex-M35P | No | No | No |`cortex-m35p`|`+soft-float,-dsp`|
-| Cortex-M35P | No | Yes | No |`cortex-m35p`|`+soft-float`|
+| Cortex-M35P | No | No | No |`cortex-m35p`|`-fpregs,-dsp`|
+| Cortex-M35P | No | Yes | No |`cortex-m35p`|`-fpregs`|
 | Cortex-M35P | SP | No | No |`cortex-m35p`|`-dsp`|
 | Cortex-M35P | SP | Yes | No |`cortex-m35p`| None |
-| Cortex-M55 | No | Yes | No |`cortex-m55`|`+soft-float,-mve`|
+| Cortex-M55 | No | Yes | No |`cortex-m55`|`-fpregs,-mve`|
 | Cortex-M55 | DP | Yes | No |`cortex-m55`|`-mve`|
-| Cortex-M55 | No | Yes | Int |`cortex-m55`|`+soft-float,-mve.fp`|
+| Cortex-M55 | No | Yes | Int |`cortex-m55`|`-fpregs,-mve.fp,+mve`|
 | Cortex-M55 | DP | Yes | Int |`cortex-m55`|`-mve.fp`|
 | Cortex-M55 | DP | Yes | Int+Float |`cortex-m55`| None |
-| Cortex-M85 | No | Yes | No |`cortex-m85`|`+soft-float,-mve`|
+| Cortex-M85 | No | Yes | No |`cortex-m85`|`-fpregs,-mve`|
 | Cortex-M85 | DP | Yes | No |`cortex-m85`|`-mve`|
-| Cortex-M85 | No | Yes | Int |`cortex-m85`|`+soft-float,-mve.fp`|
+| Cortex-M85 | No | Yes | Int |`cortex-m85`|`-fpregs,-mve.fp,+mve`|
 | Cortex-M85 | DP | Yes | Int |`cortex-m85`|`-mve.fp`|
 | Cortex-M85 | DP | Yes | Int+Float |`cortex-m85`| None |
 
@@ -74,6 +74,13 @@ to use these flags.
 | Cortex-M85 | DP | Yes | Int |`cortex-m85`|`-mve.fp`|
 | Cortex-M85 | DP | Yes | Int+Float |`cortex-m85`| None |
 
+<divclass="warning">
+
+Never use the `-fpregs`*target-feature* with these `eabihf` targets
+as it will cause compilation units to have different ABIs, which is unsound.
+
+</div>
+
 ### Arm Cortex-M33
 
 The target CPU is `cortex-m33`.
@@ -83,7 +90,7 @@ The target CPU is `cortex-m33`.
 * enabled by default with this *target-cpu*
 * Has an optional single precision FPU
 * support is enabled by default with this *target-cpu*
-* disable support using the `+soft-float`feature (`eabi` only)
+* disable support using the `-fpregs`*target-feature* (`eabi` only)
 
 ### Arm Cortex-M35P
 
@@ -94,7 +101,7 @@ The target CPU is `cortex-m35p`.
 * enabled by default with this *target-cpu*
 * Has an optional single precision FPU
 * support is enabled by default with this *target-cpu*
-* disable support using the `+soft-float`feature (`eabi` only)
+* disable support using the `-fpregs`*target-feature* (`eabi` only)
 
 ### Arm Cortex-M55
 
@@ -106,7 +113,7 @@ The target CPU is `cortex-m55`.
 * Has an optional double-precision FPU that also supports half-precision FP16
  values
 * support is enabled by default with this *target-cpu*
-* disable support using the `+soft-float`feature (`eabi` only)
+* disable support using the `-fpregs`*target-feature* (`eabi` only)
 * Has optional support for M-Profile Vector Extensions
 * Also known as *Helium Technology*
 * Available with only integer support, or both integer/float support
@@ -125,7 +132,7 @@ The target CPU is `cortex-m85`.
 * Has an optional double-precision FPU that also supports half-precision FP16
  values
 * support is enabled by default with this *target-cpu*
-* disable support using the `+soft-float`feature (`eabi` only)
+* disable support using the `-fpregs`*target-feature* (`eabi` only)
 * Has optional support for M-Profile Vector Extensions
 * Also known as *Helium Technology*
 * Available with only integer support, or both integer/float support